In the analysis of ability structure and loss of vision, 228 blind persons (153 male, 75 female) heterogenous in respect to chronological age, sex, degree of blindness, age at onset, and duration, were compared to sighted controls. A test battery was administered which included tests for verbal comprehension, mental arithmetic, spatial ability, arithmetic reasoning, memory, dexterity, kinesthetic memory, and tactual discrimination. Factor analysis indicated the following: blindness did not hinder the differentiation of mental abilities; tests which formed a visualization factor with the sighted determined a factor when performed tactually by the totally blind; and visual and spatial tests performed by the sighted, the first normally and the second tactually, formed two wholly independent factors. Also, for the totally blind, the mutually analogous tests measuring tactual and auditory discrimination sensitivities formed a factor on their own; for the partially sighted, the two correlated significantly negatively with each other. A larger proportion of the variance of test performances of the blind was due to the memory for meaningless, rather than meaningful, word pairs. (LE)