We undertook a retrospective cohort study comparing infection in solid organ transplant recipients receiving alemtuzumab (n = 726) versus basiliximab (n = 215) or antithymocyte globulin (ATG) (n = 85). Eighty-one percent of patients had kidney transplants. Overall, 33% of patients in the alemtuzumab group (240/724) developed infection compared with 40% (87/215) in the basiliximab group (odds ratio [OR], 0.72; 95% confidence interval [CI], 0.53-0.99; P = .04). The frequency of infection was similar in the alemtuzumab and ATG groups (33% versus 36%, respectively, P = .53). The frequency of fungal infections, most caused by Candida spp., was similar in the alemtuzumab and basiliximab groups (10% versus 9%); disseminated fungal infection occurred in 68% of the patients with fungal infection receiving alemtuzumab and in 30% of the patients with fungal infection receiving basiliximab (OR, 4.76; 95% CI, 1.58-14.28; P = .003). Basiliximab posed a higher risk than alemtuzumab for infection. Disseminated candidal infections were more common in patients receiving alemtuzumab.