A total of 207 skin scrapings were prospectively studied using potassium hydroxide (KOH), calcofluor white (CW), and culture to determine the clinical usefulness of each microscopic method. For dermatophytes (prevalence 13.2%), CW had a sensitivity of 92% and a specificity 95%, giving a positive predictive value of 74% and negative predictive value of 99%. KOH had a sensitivity of 88% and a specificity of 95%, giving a positive predictive value of 73% and a negative predictive value of 98%. CW was simple, rapid, and easy to read. For dermatophyte infection, CW results are as useful as KOH results.