The effect on achievement of sequential organization of subject matter in programed instruction, the interaction of sequence with verbal ability, and the effect of two types of anxiety on learning were examined in this study. Subjects were randomly assigned to either a group in which program frame sequence had been scrambled by means of a table of random numbers or to a group in which the program frames were logically sequenced. Two programs dealing with heart disease were employed: one program contained material of some familiarity to the subjects and the other contained technical content which was new to the subjects. The results indicated that, as expected, the type of sequence caused significant differences in achievement on the unfamiliar materials but not on familiar content. Interactions between sequence and verbal ability were not found, though there was some evidence for triple interactions among sequence, verbal ability, and anxiety. The results provided further evidence that a pupil's prior familiarity with subject matter may be an important moderating variable in determining which instructional mode or type of content organization leads to superior achievement. (Author/JY)