We report a case of familiar retinoblastoma, in which both mother and daughter show bilateral retinoblastoma. The cytogenetic study, in both peripheral blood lymphocytes and tumoral tissue did not show alterations on the 13 chromosome, although we found a complex kariotype in tumoral tissue defined by three celular lines. In all of them appears a marker in which the 6 chromosome is involved (der 6). The derivated of 6 chromosome are markers highly characteristic of the retinoblastoma cases, and can be related with the aggressivity of tumor and the appearance of the second tumors.