A study compared the oral and written language concepts of preschoolers from low- and middle-income homes. Subjects, 33 4-year-olds from 3 separate Head Start programs and 31 4-year-olds from three different private schools, were administered 9 informal language assessments in the fall and again in the spring. Parents of the subjects were interviewed. Results indicated that: (1) children from middle-income homes outperformed their low-income counterparts in knowledge of language on eight of the nine variables in the fall; (2) in the spring, the performance of middle-class preschoolers was superior to their low-income cohorts on all nine variables; (3) the percentage of the low-income subjects in the top quartile dropped from 25% in the fall to 7% in the spring; (4) the percentage of the low-income subjects in the bottom quartile rose from 71% in the fall to 92% in the spring; (5) low-income parents reported fewer books, infrequent reading to children, and virtually no encouragement for engaging in reading and writing activities; (6) four of the middle-income subjects and one lower-income subject were able to read; and (7) differences in subjects' knowledge of identifying environmental print and recognizing readable print were not significant. Findings suggest that even as early as 48 months of age, children from low-income homes are at a distinct disadvantage when compared to their middle-class peers on many language concepts, and fall further behind them by the end of preschool. (Two tables and one figure of data are included; 27 references are attached.) (RS)