Seven-year-old triplets with autism displayed off-task behavior that threatened their continued placement in a general education first-grade classroom. A descriptive Functional Behavioral Assessment (FBA) was conducted for each student. Data from structured interviews and direct observations were used to identify the functions of their off-task behaviors and to design a comprehension function-based intervention. Task analyses of the students' replacement behavior provided empirical data for deciding whether each student needed specific instruction to independently perform the replacement behavior. The intervention was systematically implemented during typical classroom activities for five weeks and follow up data were collected for an additional three weeks. The intervention improved each student's behavior and the effects maintained during follow up. Social validity ratings by all staff members were high.