This secondary data analysis from a Head Start program examines the association between children's entry age and enrollment duration and the likelihood of mental health treatment. Study questions are as follows: (a) Do baseline characteristics differ among three groups of Head Start children? (children who enrolled at 3 years of age and stayed for 1 year [group 1], enrolled at 4 years of age and stayed for 1 year [group 2], and enrolled at 3 years of age and stayed for 2 years [group 3]); (b) Does the likelihood of children's mental health treatment differ among the groups?; and (c) Are baseline characteristics associated with the likelihood of mental health treatment? Except ethnicity and family size, other baseline characteristics did not differ across the three groups. Groups 1 and 3 received more mental health treatment than group 2. Different percentages of mental health treatment were found, depending on children's gender, ethnicity, family income, special needs, and bilingual status. (author abstract)