Intravenous dipyridamole planar thallium-201 imaging is a safe and effective test for detection and prognosis of coronary artery disease (CAD) in the general population. The relative diagnostic accuracy and side-effect profile of dipyridamole thallium-201 stress imaging in women is not defined. Forty-three consecutive female and 71 male patients who underwent dipyridamole thallium-201 imaging (0.56 mg/kg) within 3 months of cardiac catheterization were studied. Scans were considered abnormal if fixed or reversible perfusion defects were detected. Stenosis severity of greater than or equal to 50% luminal diameter reduction of any artery defined CAD. Overall sensitivity for detection of CAD was 0.87 in women and 0.94 in men; specificity was 0.58 in women and 0.63 in men (p = not significant). Sensitivity for detection of 1-vessel CAD was 0.60 in women and 0.94 in men (p = 0.001). The sensitivity for detection of multivessel CAD (with or without surgical revascularization) was 1.0 and 0.94 in women and men, respectively. Adverse effects were reported in 62% of women and in 38% of men (p = 0.01). There was no significant difference in the incidences of chest pain, headache, nausea, flushing or electrocardiographic changes. The incidences of severe ischemia and dizziness were higher in women. Possible explanations for this difference in adverse effects include gender differences in the volume of distribution of dipyridamole due to varied fat-to-muscle ratios and different subjective nocioceptive sensitivities to the effects of dipyridamole. Overall sensitivity and specificity are comparable between the sexes.