Predictive relations were examined between measures of 20 mothers' behavioural and verbal general and specific responsiveness and intrusive and supportive directiveness and their children's subsequent expressive vocabularies during three developmental periods with endpoints at the beginning, middle, and end of the second year: 0;10 to 1;1, 1;1 to 1;5, and 1;5 to 1;9. Regression analyses, controlling for mothers' utterance frequencies and children's initial lexicons, revealed considerable consistency between reported and observed lexicons but changing patterns of predictive relations with development. During the first period, behavioural, but not verbal, measures of maternal responsiveness and supportive directiveness were positively predictive. In period two, verbal, but not behavioural, measures predicted children's vocabularies, with specific responsiveness and supportive directiveness as positive predictors and intrusive directiveness as a negative predictor. During the final period, mothers' behavioural and verbal responsiveness and behavioural supportive directiveness positively predicted and their verbal intrusive directiveness negatively predicted children's lexical growth.