The task of developing prognoses for late-talking children has long been a challenge for speech-language pathologists, developmental psychologists, and pediatricians. Improved predictors would help to assess long-term risk and determine appropriate intervention services. The present study evaluated children's length of longest utterances (LLU) as a predictor of mean length of utterance (MLU) one year later. Relationships between LLU at 30 months, MLU at 30 months and MLU at 42 months were examined in 43 late talkers (LT) and 33 age-matched children whose language was typically developing (TD). LLU was a significant predictor of MLU at 42 months with particularly strong correlations within the LT group. Similar results were obtained when controlling for language sample size, which was positively related to LLU. For the LT group, a regression model combining 30-month LLU and MLU was better at predicting 42-month MLU than 30-month MLU alone. The results are discussed in terms of frequency distributions of utterance lengths within language samples.