This study addressed the issue of social support for patients' adherence to medical regimens. Social support of wives was assessed by structured interview of 150 male participants in the Coronary Primary Prevention Trial, their wives, and medical staff. In addition, wives were interviewed about their beliefs related to their husbands' health and participation in the trial. Unobtrusive packet counts were used as the measure of adherence. The participants were classified as having high spouse support if wife support scores were in the top one third of the distribution and as having low spouse support if scores were in the bottom one third as measured from inquiry of the participant, the spouse, and the staff. The adherence of men having low support averaged 70 percent, significantly lower than the high-support group, which averaged 96 percent. The correlations between spouses' health beliefs and their level of support were significant for three of four health belief variables. In particular, highly adhering men had wives who believed more strongly in the benefits of the Coronary Primary Prevention Trial.