Juvenile xanthogranuloma (JXG) is an uncommon non-Langerhans cell histiocytosis. We investigated 148 biopsy specimens from 129 patients collected in the Kiel Pediatric Tumor Registry (KPTR) between 1965 and 2001. The clinical, histologic, and immunohistochemical characteristics of JXG were evaluated to gain more and deeper insights into the morphology and clinical behavior of JXG. Conventionally stained lesions were classified into the following morphologic subtypes: early JXG (EJXG), classic JXG (CJXG), transitional JXG (TJXG), or combined lesions with more than one basic pattern (combined JXG). Immunohistochemistry included antibodies against macrophages (Ki-M1P), S-100 protein, CD1a, and factor XIIIa (FXIIIa). Clinical data were obtained by means of a standardized questionnaire. The relative incidence of JXG in the KPTR is 0.52%. The male/female ratio was 1.4:1. The mean age was 22.4 months (median, 5 months; range, 0-244 months). A total of 34.5% of the cases of JXG were congenital, and 71.0% of the lesions were diagnosed within the first year of life. Most cases of cutaneous JXG were solitary (81.0%). Five cases (3.9%) presented with visceral (systemic) involvement. Histologically, CJXG was most frequent (47.2%), followed by EJXG (27.1%) and TJXG (16.0%). A total of 9.7% of the lesions represented combined JXG. Histiocytes, including giant cells, were positive for Ki-M1P (100%) and in most cases for FXIIIa (99%). The CD1a and S-100 protein reactions were generally negative. Clinical and follow-up data showed a generally favorable prognosis with a low relapse rate (7.0%) and even complete involution after incomplete resection. Only 1 of 5 patients with widespread congenital systemic disease died after 34 days. JXG is an uncommon, mostly cutaneous, and prognostically favorable histiocytic tumor of infancy. Simple tumor excision is the therapy for choice except in the very rare systemic JXG, in which multimodal chemotherapy is indicated.