Short-term memory (STM) functioning of young and older adults was studied in two experiments in which recall and recognition tasks were used. The stimuli consisted of simple and complex visual patterns which were subject paced (Exp. I) or paced (Exp. II). Sex and response delay were the other independent variables. Age-related decrements in visual STM were observed. They interacted in a complex manner with the other variables suggesting age-related deficits at the encoding and post-encoding but not the retrieval phases. The results were discussed with reference to the locus of age related STM deficits.