This study focuses on morphophonology and frequency in past tense production. It was assessed whether Dutch five- and seven-year-old typically developing (TD) children and eight-year-old children with specific language impairment (SLI) produce the correct allomorph in regular, irregular, and novel past tense formation. Type frequency of the allomorph, token frequency and phonotactic probability (PP) of the novel verb form are considered. The results showed all groups were sensitive to the phonological cue. PP did not contribute to past tense inflection of novel verbs in any of the groups, but type frequency did in all three groups. Only the seven-year-old typically developing children relied on token frequency for inflection of regulars. The findings point to an important role of phonology and frequency in past tense acquisition for both TD children and children with SLI. We discuss how the SLI performance pattern relates to theories on SLI.