We analysed the in vitro binding of p53 from normal (3T3) and from chemically transformed (Meth A) Balb/c mouse cells to double-stranded (ds-) DNA and to single-stranded (ss-) DNA by DNA-cellulose chromatography. We confirm previous findings that p53 in cellular extracts exhibits ds-DNA-binding activity (Lane and Gannon, 1983). In addition, we demonstrate that such p53 also binds to ss-DNA. Analyses with immunopurified p53 protein provide evidence that this DNA-binding activity is intrinsic to p53. DNA binding of p53 could not be inhibited by a monoclonal antibody specific for the C-terminal region. An N-terminal deletion mutant of p53 (Rovinski et al., 1987) exhibited similar DNA-binding properties as wild-type p53, indicating that the N-terminus also is dispensable for DNA binding. We further show a close correlation between the DNA-binding activity of p53 from 3T3 cells and its association with nuclear substructures.