The dedifferentiation hypothesis is examined with respect to age-group differences, ability-group differences, attrition-group differences, and time. Cognitive and sensory data were analyzed from individuals (n = 1,823) who completed a clinical assessment on at least 1 of 3 occasions of measurement in the Australian Longitudinal Study of Ageing. Inconsistent dedifferentiation effects were associated with low ability and early attrition from the study, but age-related dedifferentiation was not found. Longitudinal analyses confirmed the cross-sectional analyses. Even though instances of dedifferentiation were identified between pairs of sensory and cognitive variables, consistent patterns of dedifferentiation were not found. These results do not support the view that shared biological factors become increasingly important for explaining within-individual change in cognitive and sensory function in later life.