Single base pair germ-line deletion in the p53 gene in a cancer predisposed family. A family with an aggregation of adrenocortical carcinoma, rhabdomyosarcoma, osteosarcoma, and early onset breast cancer was referred to our laboratory. Because this aggregation was reminiscent of Li-Fraumeni syndrome, germ-line mutation of the p53 tumor suppressor gene was sought in the DNA of two affected members. The highly conserved regions spanning exons 5 to 8 of the p53 gene were screened by a previously validated denaturing gradient gel electrophoresis method. A single base pair deletion at codon 215 was detected in constitutional DNA of the two patients, and in the DNA extracted from an adrenocortical carcinoma tumor specimen of the propositus. This deletion is predicted to lead to the formation of a truncated p53 protein, a relatively rare event in Li-Fraumeni families. The spectrum of tumors observed in this family does not differ markedly from the spectrum observed in families with missense p53 mutations.