Family studies require assessment of large numbers of family members, many of whom are geographically dispersed, live in different time zones, are not available during working hours, live in neighborhoods which are unsafe, or do not wish to have attention drawn to them by the presence of an interviewer in their home. For these reasons, telephone interviews are a potentially valuable and economical method. We present a comparison of results from telephone and face-to-face interviews conducted with 435 relatives of 193 probands from a family study. No significant differences were found between telephone versus face-to-face interviewed relatives in rates of RDC or of DSM-III-R diagnoses. Nor were differences found in the length of interviews; number of family history reports completed; or number of relatives requiring consensus diagnoses due to diagnostic disagreement. We conclude that telephone and face-to-face interviews yielded comparable diagnostic information in this family study and that telephone interviewing is an acceptable and valuable alternative method for the diagnosis of lifetime psychiatric disorder in relatives.