Both administratively and in terms of their evaluations, Head Start and Follow Through have been treated as separate programs. Follow Through was initially conceived, however, as an effort to preserve and augment Head Start gains. In this report, achievement test data on a set of children who participated in both Head Start and Follow Through are used to determine if Follow Through helps maintain the benefits of Head Start in the early elementary grades, and how the Head Start experience of children may have confounded efforts in the national evaluation of Follow Through to calculate program effects. Regarding the maintenance of benefits, Follow Through does maintain increased test scores on skills measured through the end of kindergarten. There are, however, no overall effects on skills measured in later grades. As for the question of measurement problems, there is probably a bias operating against Follow Through in general, and particularly in sites where the Follow Through group has a much higher proportion of Head Start children than the Non-Follow Through group. This bias is not overwhelming, but may be large enough to change the outcomes significantly for many sites. In addition, the design for data collection in Follow Through severely limits the ability to investigate how Follow Through has affected children's growth. Ignoring Head Start, and using one pre-test and one post-test forces a great burden on statistical adjustments. In retrospect, it would have been preferable to rely less on statistical manipulations of the data and more on tracing data for individual children across several time points. (Author/CP)