In the present study histologic, clinical and follow-up data of 37 cases of retinoblastoma were statistically analyzed by means of a multivariate method. The evaluated histological parameters were: growth pattern, degree of differentiation, number of mitoses, presence of necrosis, pseudorosettes, blood vessel basophilia, calcification, extension to anterior chamber, invasion of optic nerve and ocular coats (choroid and sclera). The analysis was based upon the Cox proportional hazards regression model. Invasion of ocular coats proved to be highly correlated to the prognosis (p less than 0.0002). None of the other parameters showed a significant relation to survival.