The techniques used for fine needle aspiration biopsy of 19 intraocular tumors clinically suspected to be malignant melanomas are described. Aspirates of 16 tumors yielded adequate material for the cytologic diagnosis of malignant melanoma. Malignant cells of the epithelial type and of a spindle shape were found in the smears. The main cytologic features of the epithelial-type cells were eccentrically located nuclei, distinct nucleoli, binucleation and multinucleation. The spindle-shaped cells, dispersed or arranged in clusters, were characterized by centrally placed, oval or rodlike nuclei, with or without nucleoli. Three types of smears were distinguished: (1) those with a predominance of epithelial-type cells, (2) those with a predominance of spindle-shaped cells and (3) those with mixed epithelial-type and spindle-shaped cells. Our observations prove that precise morphologic diagnosis of intraocular malignant melanoma and its cellular types can be established by fine needle aspiration biopsy. However, we do not advocate fine needle aspiration biopsy as a routine diagnostic procedure in all intraocular melanomas. This method should be reserved for only cases that cannot be definitely diagnosed by conventional techniques or in which the cellular type of melanoma must be defined in order to choose the proper method of treatment.