We report on 26 infants under 3 months of age with various liver tumors, who were treated in our hospital since 1977 and/or registered in the German Cooperative Pediatric Liver Tumor Study HB-89. 17 of these had an infantile hemangioendothelioma (inf HE), 7 a hepatoblastoma (HB), one a mesenchymal hamartoma (mes H) and one a neuroblastoma stage IV-S (Nbl). Polyhydramnios occurred in 5 cases of inf HE, in one associated with hydrops fetalis. This led to a preterm delivery of 4 infants. 7 infants with a large inf HE suffered from high output congestive heart insufficiency, 2 additionally from a Kasabach-Merritt-syndrome. Serum alpha-fetoprotein was within normal range of age in all infants except in one HB patient. Neuron-specific enolase was clearly elevated in the Nbl patient and slightly above normal range in one inf HE and 3 HB patients. Other tumor markers and platelet counts were not indicative of diagnosis. Also imaging techniques as ultrasonography, CT and angiography were not always reliable in differentiating the tumors. In 2 cases the initial histological diagnosis of an HB had to be corrected for an inf HE. In 6 children the tumors were initially treated under a wrong assumption: 4 tumors as an HB instead of an inf HE, one as an inf HE instead of a Nbl IV-S and one as a focal nodular hyperplasia of the liver instead of an HB. 7 not resected inf HEs (Dehner type I) showed spontaneous regression after 6 months to 3 years. One inf HE type II relapsed twice after resection.(ABSTRACT TRUNCATED AT 250 WORDS)