OBJECTIVE To prospectively evaluate complications after diagnostic and therapeutic endovascular procedures (DTEPs) and determine what factors are predictive. METHODS From December 2002 to December 2003, all patients undergoing DTEPs performed by university vascular surgeons in a catheterization laboratory were prospectively evaluated. Medical demographics, procedure-related details, and type and severity of complications were recorded at the time of the procedure, during the first 24 hours, and at 2 to 4 weeks. Complications were classified as local vascular (LV), local nonvascular (LNV), systemic remote (SR), and major, minor, and nonsignificant. RESULTS Three hundred-three DTEPs were performed (54.5% DEPs, 45.5% TEPs). At the time of DTEP, 28 complications occurred in 23 patients: 10 LV (3.3%), 15 LNV (5.0%), and 3 SR (1.0%). At 24 hours, 26 complications occurred in 25 patients: 5 LV (1.7%), 7 LNV (2.3%), and 14 SR (4.7%). At 2 to 4 weeks, 26 complications occurred 25 patients: 5 LV (1.7%), 7 LNV (2.3%), and 14 SR (4.7%). The combined major (7.3%) and minor (4.3%) complication rate attributed to DTEPs was 11.6%. Significant predictors (P < .05) by multivariate analysis included thrombolysis, prior stroke, an additional procedure during the study period, and diabetes mellitus (odds ratios: 9.1, 3.2, 2.7, and 2.4, respectively). CONCLUSION According to newly applied reporting standards, the prospective evaluation of DTEPs reveals that complications are uniformly distributed by type and follow-up period. Just over 1 in 10 patients will suffer either a major or minor complication. Potential predictors have been identified that may assist in patient selection and treatment plans to lower complications resulting from DTEPs.