A survey in a London borough showed that 15% of adults living at home were restricted in one or more areas of their lives because of illness. A sample of these adults aged 25 to 75 years was interviewed using a validated medical questionnaire, and the severity of their restrictions was also assessed using a separate instrument. Many symptoms were found which had not been reported to a doctor and many were not being treated. When the disability scores were regressed on symptoms classified as reported to a doctor, unreported, or absent, with a few exceptions it was the reported symptoms that were significantly associated with disability. Similarly, when symptoms were classified as treated (by doctor or respondent), untreated, or absent, treated symptoms were associated with disability. Some disabling symptoms were similar to the effects, mainly adverse, of commonly prescribed drugs, and these symptoms were reported more frequently by respondents taking the possible offending drug than by those not taking the drug. It appears that making general practitioners aware of unreported and untreated symptoms among their 25 to 75 year old patients will not reduce the overall level of disability in the community. However, the iatrogenic component of disability needs to be studied further.