As part of a Feelin' Good intervention program to improve the physical fitness of children in grades 2 through 4, 603 students were tested for muscle strength and flexibility. Complete pre- and posttest data were obtained from 388 students. Two muscle strength tests and two flexibility tests demonstrated consistent sex differences in performance. Three muscle strength tests demonstrated grade level differences: older girls outperformed younger girls. Fourth grade boys exhibited a pattern of depressed performance on two flexibility tests. Using McNemar's (1969) test of the differences of correlated proportions, performance changes from pre- to posttest were assessed. Both boys and girls showed significant improvement on two muscle strength tests and two flexibility tests. Results indicate a pattern of improvement in performance from pre- to posttest. It was concluded that intervention programs make a difference, but schools should not be dependent upon outside sources to teach health and physical education. (Author/RH)