To determine risk factors, seasonality, and trends of cryptosporidiosis among human immunodeficiency virus-positive (HIV+) patients in the New Orleans area, data from the New Orleans component of the Adult/Adolescent Spectrum of HIV Disease Study (ASD) were analyzed. A total of 6,913 HIV+ patients ≥ 13 years of age were enrolled in the ASD database between 1990 and 1998. After an average follow-up of 42 months, cryptosporidiosis had been diagnosed in 239 patients (3.5%). The risk of developing cryptosporidiosis was higher among patients with CD4+ cell counts < 100 x 106/L, among those who ever developed an acquired immunodeficiency syndrome (AIDS)-opportunistic illness, and among patients < 35 years old compared with their counterparts. A slight increase in cryptosporidiosis cases occurred in the spring compared with other seasons, but the difference was not statistically significant (P > 0.05). The prevalence of cryptosporidiosis increased from 2.9% (n = 7) in 1989 to 20% in 1994 (n = 48) before decreasing to 5.3% in 1998 (n = 14). Since a fair number of cryptosporidiosis cases are still being reported in the New Orleans area after the introduction of highly active antiretroviral therapy, further studies are needed to provide insight into the existence of potential environmental sources of Cryptosporidium.