Purpose: This study examined whether lexical frequency, semantic knowledge, or sentence context affect children's production of primary stress in derived words with stress-changing suffixes (e.g., "-ity"). Method: Thirty children (M[subscript age] = 9;1 [years;months]) produced a limited set of high-frequency (HF) and low-frequency (LF) derived words formed with stress-changing suffixes (e.g., "-ity"). Half of the children produced the derived words in a sentence context. The other half produced words in isolation. Semantic knowledge of the derived words was also assessed. Results: Primary stress was produced more accurately in HF words than in LF words. HF words produced in a sentence context were more accurate than all LF words and HF words produced in isolation. Both knowing a word's meaning and accurately producing stress was more likely for HF words than for LF words. A substantial minority of derived words (36%) was either known semantically or produced correctly, but not both. Conclusion: Accurate morphophonological production may involve semantic and frequency factors, but those factors alone do not explain all of the results. This study isolates several important factors that may be useful when choosing derived word stimuli. (Contains 4 tables, 1 figure, and 1 footnote.)