OBJECTIVE To examine the trajectory of uncertainty and symptoms of psychologic stress during the first 3 months after coronary angioplasty and coronary bypass surgery and to study the impact of social support on uncertainty and psychologic stress in these patient populations. METHODS Descriptive, correlative. METHODS Urban community, at-home interviews. METHODS Male patients with angioplasty (n = 22) and bypass (n = 25) at 1 and 3 months after treatment. Age range was 39 to 75 years (mean 58 years). METHODS Mishel Uncertainty in Illness scores, General Health Questionnaire scores, and Perceived Social Support Scale scores. METHODS Patients underwent either percutaneous transluminal coronary angioplasty or coronary artery bypass grafting as treatment for coronary artery disease. RESULTS Data were analyzed with repeated measures analysis of variance and Pearson correlation coefficients. Results showed that at both time periods angioplasty patients were more uncertain than bypass patients (p < 0.05), and that regardless of procedure, patients reported fewer symptoms of psychologic stress at 3 months than at 1 month (p < 0.01). Patients with high social support had less uncertainty and psychologic stress than patients with low support (p < 0.05). Analysis of the social support and treatment group interaction showed that angioplasty patients with low perceived social support had significantly more psychologic stress than angioplasty patients with high support (p < 0.01). Analysis of the correlations between uncertainty and psychologic stress in the angioplasty and bypass grafting procedure groups after control for social support revealed that social support was a significant mediator of the relationship between uncertainty and stress only among patients undergoing percutaneous transluminal coronary angioplasty. There was little evidence of a mediating role for social support in the coronary artery bypass grafting group. CONCLUSIONS These results suggest that angioplasty patients may be in particular need of interventions aimed at reducing uncertainty, and that interventions that increase social support could be important in achieving this reduction.