Background: Renal allograft transplantation is associated with an increased incidence of malignant melanoma. The development of excess melanocytic nevi may be an indicator of this risk. Objective: This study determines the prevalence of melanocytic nevi in children who have received renal allografts. Methods: Total and regional melanocytic nevi counts were made in 38 children (27 boys, 11 girls) with a renal allograft and in 38 individually age- and sex-matched healthy controls; counts were related to age, sex, skin type, and duration of immunosuppression. Results: There was a significant increase in the total number of nevi in the renal transplant group compared with the control group ( p < 0.05), with most marked increases occurring on the back and at acral sites. A strong positive correlation between nevi count and duration of immunosuppression independent of age was observed ( p < 0.005). Conclusion: Excess numbers of melanoeytic nevi occur in children with renal allografts. These patients constitute a risk group for malignant melanoma and require continued assessment.