Sleep behavior has been related to both child and environmental factors, but the relative importance of these factors is not yet clear. This study was an examination of the relation of diurnal sleep patterns to perinatal risk, infant temperament, home environment, parenting stress, emotional support, and social class. Twenty-three adolescent and 23 single adult mothers and infants were assessed in the home at 4 and 12 months. Percent sleep during the night was most strongly related to parenting stress and variability of night sleep to emotional support. Emotional support mediated effects of stress at 4 months. Results support the value of clinical assessment of sleep behavior.