Disadvantaged children attending a high-quality, government-run intervention program were compared with children attending other day care programs of varying quality on intellectual, language, and social skill. Thus, quality serves as a proxy for treatment intensity here. Although the intervention children had less intelligent mothers of lower occupational status, they were rated by their caregivers as having better communicative skills and were rated by both their parents and their caregivers as more considerate and more sociable than children attending other day care programs. There were no differences between the two groups on ratings of maladjustment or dependency. When the intervention children were compared to children of similar family background, these findings held, and, in addition, the intervention children had higher scores on both the Peabody Picture Vocabulary Test-Revised (PPVT-R) and the Preschool Language Assessment Instrument. Thus, high-quality day care can function as an effective intervention. Effect-size estimates are compared with those from five other day care intervention programs. The present study concludes with a discussion of four considerations that should guide both our interpretation of existing data and our plans for future research: (1) program type, (2) intervention participants, (3) quality of the evaluation, and (4) long-term vs. short-term effects.