Three experiments investigated the ability of eight-year old children with poor language comprehension to produce past tense forms of verbs. Twenty children selected as poor comprehenders were compared to 20 age-matched control children. Although the poor comprehenders performed less well than controls on a range of tasks considered to tap verbal-semantic abilities, the two groups showed equivalent phonological skills. Poor comprehenders performed as well as control children when asked to inflect novel verbs and regular verbs. In contrast, poor comprehenders were less skilled than controls at inflecting both high frequency and low frequency irregular verbs. Although the predominant error pattern for all children was to over-regularize, this was most marked in the poor comprehenders; control children were more likely to produce errors that contained knowledge of the irregular form than poor comprehenders. In addition, the ability to inflect irregular verbs was related to individual differences in verbal-semantic skills. These findings are discussed within a framework in which verb inflection is related to underlying language skills in both the phonological and semantic domains. [This research was conducted with support from the Wellcome Trust .]