This study was undertaken to characterize nutritional vulnerability among a sample of homeless youth in downtown Toronto. Interviews were conducted with 261 homeless youth (149 male, 112 female), recruited from drop-in centers and outdoor locations. Information about current living circumstances, nutrition and health-related behaviors, and 24-h dietary intake recalls were collected, and height, weight, triceps skinfold thickness, and mid-upper arm circumference were measured. A second 24-h dietary intake recall was conducted with 195 youth. Youth's energy intakes approximated the requirements for a very sedentary lifestyle; 7% were underweight and 22% were overweight or obese. Over half of the youth had inadequate intakes of folate, vitamin A, vitamin C, magnesium, and zinc; in addition, more than half of females had inadequate vitamin B-12 and iron intakes. Most youth got food from more than one source in the course of a day: 74% of males and 75% of females purchased food; 48% of males and 51% of females obtained food from charitable meal programs; 47% of males and 75% of females received food from strangers or acquaintances; and 10% of males and 6% of females stole food or took it from the garbage. Compared to a sample of 114 domiciled youth from the 1997-1998 Ontario Food Survey, males had lower energy and nutrient intakes and females had lower intakes of most nutrients.