Children's literacy skills are an important predictor of success in the early elementary grades. Education programs for at-risk preschool students target children's acquisition of specific literacy skills, including knowledge of letters of the alphabet, in preparing children for early school success. Writing has been proposed as a complementary approach to other instructional strategies for teaching young children about letters. This study examines relations among preschool children's early writing competence, knowledge of letter names, sensitivity to initial sounds in words and understanding of print concepts in a sample of low-income children enrolled in Head Start. Data were collected from the beginning to the end of the school year, which offered the opportunity to examine concurrent development of these early literacy skills. Results revealed that children whose writing was more sophisticated knew the names of more letters, understood more about print concepts and were more sensitive to initial sounds of words. There was evidence of bidirectional influences of writing on growth in letter knowledge, and of letter knowledge on growth in writing competence. (Contains 4 tables and 1 figure.)