We studied the expression of laminin (Ln) chains (alpha1-alpha3, beta1-beta3, gamma1) in human renal-cell carcinomas (RCC), papillary renal neoplasms (PRN) and oncocytomas, in RCC cell lines and their xenografts. In RCCs the basement membranes (BM) showed immunoreactivity for chains of Ln-1 (alpha1-beta1-gamma1). Only in well-differentiated RCCs could vessel BMs be distinguished from those of carcinoma cell islets. RCCs and oncocytomas also exhibited an abundant immunoreactivity for Ln beta2 chain in both vessel and tumor cell BMs, while Ln alpha2 chain was not seen in any renal tumors. In distinction from RCCs, PRNs presented a strong BM immunoreactivity for Ln alpha3 and beta3 chains and for Ln-5, as well as lack of Ln beta2 chain. A more variable reactivity for Ln-5 was seen in oncocytomas. As PRNs and oncocytomas have been suggested to originate from collecting ducts, it is notable that in normal human kidney, we could detect immunoreactivity for Ln-5 and its chains only in BM of the tubules of the loop of Henle. In immunoprecipitation experiments, an abundant production of Ln-1, but not of Ln-5, was seen in cultured RCC cells, while in xenografts of the same cells BM-confined immunoreactivity for both Ln-1 and Ln-5 was seen. Ln beta2 chain was produced by 2 of the 4 RCC cell lines in culture but was found only in 1 of the xenografted tumors.