This study compared naturalistic samples of three features of language in 30 two-year-olds--total utterances, word roots, and MLU--in the home in three contrasting situations: the child observed playing by her/himself with mother near by, the child and mother observed in direct play interaction, and the child and mother unobserved at a time the mother judged would provide a sample of the child's 'optimal' language. Children produced more utterances and word roots and expressed themselves in longer MLU when in interaction than when playing 'alone', but children's utterances, word roots, and MLU were greatest in the 'optimal' language production situation. Girls used more word roots and spoke in longer MLU (especially in the 'optimal' language situation) than boys. Despite mean level differences, children maintained their rank orders across the three situations in use of word roots and in MLU. These findings have implications for understanding children's language and the representativeness of sampling child language.