Retinoblastoma (RB) is a childhood tumor of the eye with an average incidence of one case in every 15,000-20,000 live births and occurs in sporadic or hereditary form. This cancer results from loss or inactivation of the RB1 gene located at 13q14.1. This gene encodes for a 110 Kd nuclear phosphoprotein (pRB) that plays a major role in cell proliferation control. Different types of mutations in the RB1 gene have been reported, but point mutations are the most common. There are no molecular studies on RB1 gene mutation in Mexican patients. In this study, 19 patients with bilateral or unilateral RB were analyzed. Genetic and cytogenetic studies were carried out. Detection of RB1 gene mutations was done using single-strand conformational polymorphism (SSCP). Five conformational polymorphisms were identified in different exons. In all cases, SSCP sequence showed new non-described mutations that produced a frameshift on the open reading frame. The identification of mutations in the RB1 gene contributes to basic knowledge of this neoplasia and permits the possibility to offer adequate genetic counseling to relatives at risk.