The relationship between actigraphy- or diary-based sleep parameters and salivary melatonin-based dim light melatonin onsets (DLMOs) was examined in 21 adolescents with a history of substance abuse and current complaints of sleep difficulties. The adolescents displayed relationships between diary-based sleep times and DLMO that were of comparable strength with those reported for adult insomniacs and healthy adolescents during the school year, but weaker than those observed in healthy adults and healthy adolescents on summer vacation. When the sample was divided into adolescents with late and early DLMOs, the 2 groups had significantly different phase angles between DLMO and sleep variables but no other significant differences in sleep parameters. However, circadian phase and its relationship to sleep may have sleep and behavioral consequences.