BRCA1 and BRCA2 germline mutations cause a substantially increased life time risk of both breast and ovarian cancer. Mutational screening of these genes by means of Denaturing High Performance Liquid Chromatography (DHPLC) in breast and/or ovarian cancer-prone families from Southern Germany revealed 15 novel BRCA1 and 8 novel BRCA2 sequence variants. Predictions on the BRCA1/BRCA2 protein functions lead to the identification of 11 novel deleterious cancer predisposing mutations. Mutation types and their functional relevances are discussed. Our data contribute to phenotype-genotype correlation studies and to the characterisation of the mutation spectrum of BRCA1/BRCA2.