Etiology-specific profiles of intellectual abilities were compared in three groups of males with mental retardation using the Kaufman Assessment Battery for Children (K-ABC). Subjects included 10 males with fragile X syndrome, 10 with Down syndrome, and 10 with nonspecific mental retardation who were equated on both mental and chronological age. Across all three groups, sequential processing was lower than simultaneous processing or achievement, and particular subtests (e.g., Gestalt Closure) were relative strengths. Although boys with Down syndrome showed less extreme patterns of domain strengths and weaknesses, they showed a significant strength in the Sequential Processing Hand Movements subtest. In contrast, the Hand Movements subtest was lowest of all K-ABC subtests for males with fragile X syndrome. Implications were discussed for more fine-tuned research and intervention efforts.