A petrolatum and zinc oxide–based ointment containing 0.25% miconazole nitrate is reported to be effective and well tolerated in the treatment of diaper dermatitis complicated by cutaneous candidiasis (DDCC). This prospective, multicenter, open-label, long-term, phase IV study investigated the potential resistance of Candida spp. to repeated topical use of 0.25% miconazole nitrate in infants age 15 months and younger with moderate to severe DDCC. For initial and recurring episodes of DDCC over the 2-year study period, subjects were treated with a 7-day course of 0.25% miconazole nitrate ointment (active components: miconazole nitrate 0.25%, zinc oxide 15%, and white petrolatum 81.35%) with a 7-day follow-up. Clinical and mycologic evaluations were conducted before treatment (day 0) and 7 days after treatment (day 14). Potential resistance to miconazole was defined using an arbitrary breakpoint of minimum inhibitory concentration of 2 μg/mL. There was no evidence of resistance to miconazole in Candida spp. after single or repeated treatment courses of 0.25% miconazole nitrate ointment. For the initial episode of DDCC, 83 of 168 subjects (49.4%) achieved a clinical cure, 77 (45.8%) achieved a mycologic cure, and 49 (29.2%) achieved an overall cure (clinical and mycologic). The overall cure rate for recurrent episodes of DDCC was similar to or numerically greater than rates observed for the initial episode. Treatment of DDCC with 0.25% miconazole nitrate ointment was effective and generally well tolerated. No evidence of the development of resistance to miconazole in Candida spp. was observed.