Sit-Stand Option. Remand where hypothetical to vocational expert asked about jobs in which the claimant could "alternate position, sit or stand," and VE's did not state whether jobs listed were available on a part-time basis or could be performed while walking. The ALJ's report failed to clarify ambiguity in evidence of RFC. ALJ's assumptions about claimant's RFC was clearly not transmitted to the vocational expert. The hypothetical asked only about jobs in which the claimant could alternate position, sit or stand. For a vocational expert's answer to a hypothetical to be relevant, "the inputs into that hypothetical must correspond to conclusions that are supported by the outputs from the medical authorities." The ALJ must clarify the outputs by deciding what testimony will be credited and resolving ambiguities, and accurately transmit the clarified output to the expert in the form of assumptions.

Vocatoinal Factors. Stress. "Stress is not a characteristic of a job, but instead reflects an individual's subjective response to a particular situation ... Without an evaluation of Lancellotta's vocational abilities in light of his anxiety disorder, there is no basis for the ALJ's conclusion that he can perform low stress work." Stress is a factor which must be considered on an individualized basis for performing a range of work at step 5. Vocational evidence that there are a significant number of jobs in the economy that would be "low stress" for the average worker falls short of the requirements of Ruling 85-15. ALJ must undertake subjective, individualized inquiry into what job attributes are likely to produce disabling stress in the claimant, and what, if any, jobs exist in the economy that do not possess these attributes. ALJ must make subjective, individualized inquiry into nature of and what triggers claimant's nonexertional limitations. ALJ erred by failing to make findings as to claimant's ability to perform basic mental work-related activities. Although the ALJ apparently relied upon claimant's even demeanor at the disability hearing as evidence of his ability generally to work at low-stress jobs, we consider a claimant's ability to visit doctors and describe his medical problems coherently as insufficient evidence of his ability to work. Hypothetical to vocational expert is inadequate because it failed to elicit from the vocational expert any testimony directed specifically to the conditions that are likely to produce stress in the claimant. The basic mental demands of competitive, remunerative, unskilled work include the abilities (on a sustained basis) to understand, carry out, and remember simple instructions; to respond appropriately to supervision, coworkers, and usual work situations; and to deal with changes in a routine work setting. A substantial loss of ability to meet any of these basic work- related activities would severely limit the potential occupational base. This, in turn, would justify a finding of disability because even favorable age, education, or work experience will not offset such a severely limited occupational base." Social Security Ruling 85-15. The burden of showing the existence of other jobs in the national economy that the claimant can perform (Step 5) rests on the Secretary. Vocational evidence that there are a significant number of jobs in the economy that would be "low stress" for the average worker falls short of the requirements of Ruling 85-15. ALJ must undertake subjective, individualized inquiry into what job attributes are likely to produce disabling stress in the claimant, and what, if any, jobs exist in the economy that do not possess these attributes.

Even though Chronic Fatigue Syndrome POMS were promulgated after adverse ALJ decision, previous version of same section of POMS re: evaluation of Epstein Barr Virus set forth the same principles. Since historically, EBV and CFS have been used interchangeably (even though the medical evidence is questionable as to whether EBV causes CFS), as a practical matter, the EBV POMS can be applied to CFS cases. Given the uncontroverted evidence that the claimant suffered from CFS, blind reliance on a lack of objective findings is wholly inconsistent with the Secretary's policy as expressed in the POMS and in other pertinent policy statements. No need for objective medical findings. "At this point there is no 'dipstick' laboratory test for chronic fatigue syndrome;" the medical community instead uses an "operational" diagnostic procedure, so the disease is "not per se excluded from coverage because it cannot be conclusively diagnosed in a laboratory setting." The absence of definitive diagnostic tests makes it plain that the failure of some doctors to state conclusive diagnoses does not constitute substantial evidence to support a finding that the claimant did not suffer from CFS. Opinion of non-treating non-examining doctor that fatigue did not cause significant functional limitations because there was no objective abnormality found to explain the fatigue is not entitled to any weight. The amount of weight given the conclusions of non-testifying, non-examining physicians will vary with the circumstances, including the nature of the illness and the information provided the expert. The Grid is based on a claimant's exertional capacity and can only be applied when claimant's nonexertional limitations do not significantly impair claimant's ability to perform at a given exertional level. Where hypothetical to VE assumed a condition not supported by the medical evidence, the ALJ could not rely on the VE's opinion as a basis for non-disability finding.

ALJ must determine what evidence he credits in order to pose a hypothetical which will be relevant and helpful. The issue of whether or not the testimony of a medical advisor who reviews the record and testifies at the hearing can alone constitute substantial evidence varies with the circumstances, including the nature of the illness and the information provided. The testimony of a non-examining medical advisor--to be distinguished from the non-testimonial written reports in the instant case--can alone constitute substantial evidence, depending on the circumstances.