Hypotheses accounting for the pattern of deficits in specific developmental dyslexia were examined. The theory postulates that the disorder reflects a lag in maturation of the central nervous system, particularly the left cerebral hemisphere. The hypotheses in question predicted that skills developing ontogenetically earlier (visual-motor and auditory-visual integration) will be more delayed in younger dyslexic children (ages 7-8 years), and that skills developing later (language and formal operations) will be more delayed in older dyslexic children (ages 11-12 years). Subjects were 20 disabled male readers and 20 control males, all of average or above average intelligence. Each group was subdivided by age: younger (ages 7-8) and older (ages 11-12). Three tests classified as nonlanguage or perceptual and three classified as language tests were administered. The nonlanguage tests were postulated to represent skills developing ontogenetically earlier. The nonlanguage tests partially discriminated between younger dyslexics and controls, while none of the nonlanguage tasks discriminated between the older groups. By contrast, the language tasks revealed significant differences between older dyslexics and controls, while only one language measure discriminated between the younger groups, thus substantially supporting the hypotheses under evaluation. (KW)