This article presents measures of need for mental health services estimated from the 1981 Eastern Baltimore Mental Health Survey, one of five sites participating in the NIMH Epidemiologic Catchment Area Program. Data were collected on the prevalence of specific psychiatric disorders, as determined by the standardized Diagnostic Interview Schedule (DIS), functional status, personal characteristics, patterns of medical and mental health care, and sources of care used. Need is based on mental health services use in the prior 6 months or the presence of two or more manifestations of emotional problems: a) one or more DIS disorders present in the past 6 months, b) a General Health Questionnaire (GHQ) score of four or more current symptoms, or c) the respondent's report of having been unable to carry out usual activities in the past 3 months for at least 1 entire day because of an emotional problem. Approximately 14% of adults met the criteria for need, half of whom had made no mental health visits in the prior 6 months and were considered to have unmet need. Need for care was influenced by a variety of sociodemographic and economic characteristics: it was low among the aged and high among persons living alone and the poor on Medicaid. The proportion of need that was unmet varied less but was relatively large for two groups, the aged and nonwhites. Those on Medicaid through public assistance were more likely to have their need met than the near poor.