This study examined explanatory talk that occurred in families of preschool children during book readings between mother and child, and during mealtimes with the whole family. The study is part of a larger study, the Home School Study of Language and Literacy Development. Three-year-old children eligible for Head Start programs in the greater Boston (Massachusetts) area were recruited for the study. A total of 84 low-income families were visited at home once each year when the children were 3 and 4 years old. Two books, one provided by the researcher and one familiar to the child, were used for tape-recorded book reading sessions. Each mother was also asked to record family conversation during a meal. All recorded conversations were transcribed for analysis. Results indicated that a higher percentage of explanatory utterances occurred during readings of the familiar book than during readings of the experimenter-provided book. The proportion of explanatory talk during book readings was much smaller than the proportion of explanatory talk at mealtimes. When the children were 5 years old they completed a battery of standardized tests and independent language tasks. No measures of explanatory talk during book readings were associated with test outcomes. However, the amount of explanatory talk that occurred during mealtimes when the children were 3 years old was associated with some vocabulary and discourse abilities at age 5. (MM)