Recombinant adenovirus-mediated transfer of the wild-type p53 gene into monolayer cultures or multicellular tumor spheroids of human non-small cell lung cancer cell line H358, which has a homozygous deletion of p53, markedly increased the cellular sensitivity of these cells to the chemotherapeutic drug cisplatin. Treated cells underwent apoptosis with specific DNA fragmentation. Direct injection of the p53-adenovirus construct into H358 tumors s.c. implanted into nu/nu mice, followed by i.p. administration of cisplatin, induced massive apoptotic destruction of the tumors. These results support the clinical application of a regimen combining gene replacement using replication-deficient wild-type p53 adenovirus and DNA-damaging drugs for treatment of human cancer.