The authors performed a case-control study of risk factors for suprachoroidal expulsive hemorrhage (SEH); the study involved 68 SEH cases at their institution from 1981 to 1986. The authors examined 113 variables in the study group and a procedure-matched control group of 217 patients randomly selected from the 35,459 patients who underwent intraocular surgery during this period, and subjected them to bivariate and conditional logistic regression analysis. The incidence of SEH was 0.19% overall, 0.16% for lens-related procedures, 0.15% for glaucoma surgery, 0.41% for retinal and vitreous procedures, and 0.56% for keratoplasty. Statistically significant risk factors for SEH in age-adjusted bivariate analyses included: glaucoma (P less than 0.0001), increased axial length (P less than 0.0001), elevated intraocular pressure (IOP) (P less than 0.0001), generalized atherosclerosis (P = 0.007), and elevated intraoperative pulse (P = 0.0001). Conditional logistic regression analysis with frequency matching on age identified significant independent risks associated with a history of glaucoma, elevated IOP, increased axial length, and intraoperative tachycardia. One of the models predicts a 752-fold increased theoretical relative risk of SEH for a patient with axial length greater than or equal to 25.8 mm, a history of glaucoma, preoperative IOP greater than 18 mmHg, and intraoperative pulse greater than or equal to 85 beats per minute. The visual outcome after SEH was best in cases of extracapsular cataract extraction (ECCE), compared with other procedures. Results suggest that attention to multiple preoperative and intraoperative ocular and systemic variables may allow identification and prophylaxis of patients at risk for SEH.