Several families segregating the autosomal dominant form of the hereditary retinoblastoma predisposition gene have been analysed for the causative mutation. We have used the single-strand conformation polymorphism (SSCP) technique to screen for mutations, exon by exon, in the RB1 gene in affected patients from these families. The SSCP technique has proved a rapid and simple technique which relies on the sequence-dependent migration of single-stranded DNA in a non-denaturing polyacrylamide gel. Oligonucleotide primers flanking all 27 exons and the promoter region of the RB1 gene are reported here. The polymerase chain reaction (PCR)-amplified products range in size from 212 to 625 bp and include a flanking intron sequence which allows detection of mutations in these regions. The sensitivity of SSCP is optimal when DNA fragments are approximately 200 bp long. Consequently, restriction enzyme sites for each amplified region were identified, reducing the size of the PCR products analysed to less than 250 bp. Bands with aberrant migration patterns were observed on SSCP gels in the lymphocyte DNA from two patients with bilateral, familial retinoblastoma. Sequence analysis of these DNA fragments revealed the causative mutations. These consisted of a 1-bp insertion of a T in the coding strand of exon 20 and a G----A mutation in the coding strand of exon 14. This approach has proved to be a powerful method for the rapid detection of germline mutations in the RB1 gene, a programme which can be extended to individuals with new mutations.