PURPOSE: This study examined the effect of socioeconomic status (SES) on the early lexical performance of African American children. METHOD: Thirty African American toddlers (30 to 40 months old) from low-SES (n = 15) and middle-SES (n = 15) backgrounds participated in the study. Their lexical-semantic performance was examined on 2 norm-referenced standardized tests of vocabulary, a measure of lexical diversity (number of different words) derived from language samples, and a fast mapping task that examined novel word learning. RESULTS: Toddlers from low-SES homes performed significantly poorer than those from middle-SES homes on standardized receptive and expressive vocabulary tests and on the number of different words used in spontaneous speech. No significant SES group differences were observed in their ability to learn novel word meanings on a fast mapping task. CONCLUSION: The influence of socioeconomic background on African American children's lexical semantic tasks varies with the type of measure used.