OBJECTIVE: To identify predictors of the receipt of medical care, including the receipt of pre-drug screening, for diagnostically targeted fungal or mycobacterial infections among patients prescribed a tumor necrosis factor inhibitor (TNFi). METHODS: We conducted a case-control study using deidentified patient health claims information from a data set representing a commercially insured US population of 15 million patients annually from January 1, 2007 to December 31, 2009. Descriptive statistics as well as a 2-sample t-test, chi-square test of association, Fisher's exact test, and multivariate logistic regression were used for data analysis. RESULTS: A total of 30,772 patients received a TNFi during the study period. Of these, 158 patients (0.51%) developed targeted fungal and/or mycobacterial infections (cases). The median number of infections per case was 1.0 (interquartile range 1.0-2.0). Tuberculosis was diagnosed in 61% of cases, followed by histoplasmosis in 60%, nontuberculous mycobacterial infections in 11%, coccidioidomycosis in 10%, unspecified fungal infection in 8%, blastomycosis in 4%, cryptococcal infection in 3%, and pneumocystosis in 2%. Compared to controls (n = 474), a higher proportion of cases were prescribed prednisone (55% versus 37%; P < 0.001). Patients who were prescribed prednisone during the study period were twice as likely as those not taking prednisone to seek medical care attributable to a targeted fungal or mycobacterial infection (odds ratio 2.03; P < 0.001). CONCLUSION: Development of a targeted fungal or mycobacterial infection among patients taking a TNFi is rare. Concomitant use of prednisone predicted development of such infections.