Recently, a non-random transmission of BRCA1 mutant alleles to the off-spring of carriers has been suggested. If confirmed by further studies, the finding will have important implications both for risk assessment and the understanding of BRCA1 biology. However, these kind of analysis are not easy to perform due to several ascertainment biases inherent to the identification of BRCA1 carriers. In this report we propose different approaches to overcome such biases and we present additional data supporting a non-random transmission of BRCA1 mutant alleles.