Reading scores earned by 286 fifth-grade pupils taking the California Test of Basic Skills were used in a study examining the relationship between reading achievement and birth order and related family factors. Vocabulary scores were significantly related to birth order, family size, and socioeconomic status. Comprehension scores were significantly related only to family size and socioeconomic status. Sex of the student and the age span between the student and his or her nearest sibling were not related to reading achievement. (AA)