This Campbell systematic review examines the effects of linguistic comprehension instruction on generalized measures of language and reading comprehension skills. The review summarizes evidence from 43 studies, including samples of both pre-school and school-aged participants. This review considers whether language-supportive programs are effective. More specifically, the review aims to examine the immediate and long-run effects of such programs on generalized measures of linguistic comprehension and reading comprehension. The linguistic comprehension programs included in this review display a small positive immediate effect on generalized outcomes of linguistic comprehension. The effect of the programs on generalized measures of reading comprehension is negligible. Few studies report follow-up assessment of their participants.