The purpose of this study was to examine verbal fluency and verbal short-term memory in 12 adults with Down syndrome (DS) and 12 adults with Intellectual Disability (ID) of unspecified origin, matched for receptive vocabulary and chronological age. Participants' performance was assessed on two conditions of a verbal fluency test, namely, semantic and phonemic fluency. In addition to the total number of correct words produced, the use of clustering and switching strategies was also evaluated. In order to investigate the likely relations of verbal short-term memory with the test variables, a digit span task was administered. According to the results of the study, the two groups differed significantly on the average phonemic cluster size, with the ID group outperforming the DS group. Regarding the within-group comparisons, a relatively similar pattern of results was found for the two groups, indicating higher scores on all the measures involved in the semantic test than the phonemic one. The examination of the relation of verbal short-term memory with the verbal fluency test measures revealed that, in the DS group, only the total words produced in the semantic and the phonemic test and the number of phonemic switches were significantly associated with verbal short-term memory. Additionally, in both groups, word productivity in the semantic and the phonemic test was positively associated with the number of switches. The observed similarities and differences in the performance of the two groups, as well as the associations that emerged among the test variables in each group, are discussed.