We assessed the effectiveness and safety of melatonin in normalizing sleep in a 7-year-old blind child with a longstanding sleep/wake cycle disorder, using a double-masked, randomized treatment trial of placebo, a physiological dose (0.14 mg) and a supraphysiological dose (2.2 mg) of melatonin. Sleep onset and sleep offset were erratic and inappropriately early with placebo and low dose melatonin, but improved significantly on high dose melatonin. This report confirms that melatonin may be effective in treatment of disordered sleep rhythm in blind children, and illustrates a protocol that enables dose adjustment for optimal treatment response.