INTRODUCTION: Experience of the use of the Holmium: Yttrium-Aluminium-Garnet (Ho:YAG) laser in children has been limited. However, the Ho:YAG laser has been in clinical use in urology for several years but has mainly been used for the treatment of renal stones and benign prostatic hyperplasia. Due to its unique combination of vaporization and coagulation, the Ho:YAG laser allows a precise cutting action. The depth of penetration in water and tissue is limited to < 0.5 mm and therefore provides a safety margin. The Ho:YAG laser can be used in children, as the energy can be delivered via fibers that range from 200 to 1000 mu in diameter. MATERIALS AND METHODS: We used the Ho:YAG laser in 5 children (2-15 years): one child (2 years) with bladder exstrophy had a urethral stricture after bladder neck reconstruction, two children (6 years and 14 years) had ureteropelvic junction (UPJ) stenosis and refused open surgery and two children (5 years and 15 years) suffered from cystine stones (ESWL failed). The urethral stricture was incised in a retrograde fashion. We performed an antegrade incision of the UPJ with the Ho:YAG laser in the 6-year-old child and a retrograde incision in the 14-year-old child. We removed the stones in antegrade fashion in the 5-year-old child and in retrograde fashion in the 15-year-old child. RESULTS: All children now have more than 12 month's follow-up. There were no immediate or late complications. The boy with urethral stricture remained free of recurrence, the boy with UPJ stenosis obtained improved drainage on the excretory renogram and the two children with cystine stones remained stonefree. CONCLUSION: We have shown that the safety and efficacy of the Ho:YAG laser is also reproducible in urologic pathology in children. In addition, due to its vaporizing quality, the Ho:YAG laser is more effective in the treatment of cystine stones and allows minimaly invasive treatment in children.