PURPOSE: Because the usual length of time to instill two drops of cyclopentolate 1% (five to ten minutes) is time-consuming and inconvenient to clinical staff as well as to the child and the child's parents, we investigated the influence of the time interval between the instillation of the two drops on refraction and mydriasis in children. METHODS: We conducted a crossover study on 48 children at the Tel-Aviv Medical Center. Gender, iris color, ethnic origin, and age were recorded. Two cyclopentolate 1% eyedrops were instilled at a one- or five-minute time interval. Retinoscopy was performed and the mydriatic effect was recorded. One week later, the procedure was repeated, this time with a different time interval. RESULTS: The time interval between the instillation of the two drops had no significant influence on retinoscopy results (P = .65 and P = .50 for right and left eyes, respectively) or on pupil dilation (P = .377 and P = .113 for right and left eyes, respectively). CONCLUSIONS: Instilling two drops of cyclopentolate 1% one minute apart is as effective as instilling them five minutes apart.