Automatic memory processes were investigated in 10 mild and moderately retarded persons (21 years old) and in 10 chronological age-matched college level and 10 mental age-matched elementary grade control subjects through use of a frequency estimation task. This task required the subjects to view a series of slides, then estimate how many times special target items appeared in the series. Results showed that although both control groups were able to discriminate the frequency of occurrence of most target items, the mentally retarded subjects confused items occurring once with those occurring four times. Also, in most instances the mentally retarded subjects produced less accurate estimates than controls. Findings indicate that mentally retarded persons do possess some basic automatic memory processes, but these processes fail to operate as efficiently as they do in nonretarded populations. (Author/PB)