Kidney and liver tissue from eleven patients with recessively inherited infantile polycystic disease (IPCD) were examined to document the extent of renal tubular cyst formation and hepatic fibrosis, to assess survival, and to examine the usefulness of current classifications. Four infants with 90% or more cystic renal change did not survive beyond twenty days. In contrast five of the seven less severely diseased patients with a 20-75% range of cystic change are still alive at six to twenty-one years of age. Liver samples showed hamartomatous bile duct proliferation in all patients studied with the most prominent portal fibrosis in the oldest patient. In both families with two affected siblings, the clinical course and pathological expression of renal disease were dissimilar. Tissue analysis from these cases is consistent with the idea that IPCD has a spectrum of phenotypic expression with prognostic implications from tissue diagnosis in the individual patient, but not necessarily as four genetically determined rigidly defined subgroups. It is concluded that each affected child with IPCD must be evaluated separately.