We conducted the current study to determine the prevalence and clinical characteristics of vasculitis in a large series of patients with systemic lupus erythematosus (SLE), focusing on the classification and clinical significance of the different types of vasculitis. We studied 670 consecutive patients who fulfilled 4 or more of the 1997 revised criteria for SLE. Definite vasculitis was diagnosed histologically and/or by arteriography, and probable vasculitis was diagnosed clinically when there were characteristic cutaneous lesions. Vasculitides were categorized according to the definitions adopted by the Chapel Hill Consensus Conference. Seventy-six (11%) patients with SLE had vasculitis (68 female patients and 8 male; mean age, 37.8 yr); only 32 (42%) fulfilled the Chapel Hill definitions. Cutaneous lesions were the main clinical presentation of vasculitis, present in 68 (89%) patients, while the remaining 8 (11%) had isolated visceral vasculitis. Compared with SLE patients without vasculitis, patients with vasculitis had a higher prevalence of livedo reticularis (22% vs. 3%; p = 0.028); a higher mean European Consensus Lupus Activity Measurement (ECLAM) score (5.86 vs. 3.87; p < 0.001); and a higher frequency of anemia (62% vs. 17%; p < 0.001), erythrocyte sedimentation rate (ESR) >50 mm/h (60% vs. 15%; p < 0.001), and anti-La/SS-B antibodies (19% vs. 5%; p = 0.014) in the multivariate analysis. With respect to the size of the vessels involved, 65 (86%) patients had small vessel vasculitis (SVV) and 11 (14%) had medium-sized vessel vasculitis (MVV). SLE patients with MVV had a higher prevalence of mononeuritis multiplex (54% vs. 2%; p < 0.001), visceral vasculitis (100% vs. 5%; p < 0.001), and ulcerated/ischemic cutaneous lesions (36% vs. 11%; p = 0.047) and a higher percentage of surgical interventions (45% vs. 0%; p < 0.001) compared with patients with SVV. In conclusion, we observed a heterogeneous presentation of vasculitides arising in the setting of SLE, with nearly 60% of cases not fulfilling the names and definitions adopted by the Chapel Hill Consensus Conference. SVV was the most frequent vasculitis, overwhelmingly cutaneous and clearly differentiated from MVV, which was less frequent but had predominantly visceral involvement (especially of the peripheral nerves). The presence of vasculitis in our patients with SLE was associated with a higher ECLAM score, livedo reticularis, hematologic parameters (anemia, high ESR), and anti-La/SS-B antibodies.