The family genogram is generally used when the clinical situation suggests that a family assessment is warranted. Owing to the prevalence of psychosocial problems in primary care, a screening genogram that is administered to patients routinely may have a significant impact on the care provided by clinicians. A randomized controlled trial was conducted to determine the influence of screening genograms on patients' initial visits to primary care physicians. The genograms captured more information about family structure, major life events, repetitive illnesses, and family relationships than did the physicians on their own. Nevertheless, the experimental and control groups were no different on the dependent variables: physician exploration of family issues, request for interviews with other family members and counseling or referral because of emotional problems. Although the power of the study alone could account for the lack of significant results, several other methodological issues, especially contamination of the control group, could have contributed to the negative results. The results of this study are similar to those of other psychosocial screening studies using similar designs. Hence, additional studies using alternative research protocols are indicated before rejecting the usefulness of screening genograms in primary care.