Studies on speech acts represent an extensive, multidisciplinary area of research, encompassing diverse theoretical approaches such as those stemming from pragmatic, conversational, discourse, cognitive, constructional, and functional perspectives. Altogether, these theories offer an eloquent picture of the type of knowledge that is necessary to perform and understand speech acts correctly. English as a Second Language (ESL) teachers need to be aware to what extent such contemporary research findings on speech acts have made their way into present-day textbooks, and this paper sets out to elucidate this issue. First, it looks at contemporary studies on speech acts in search of the key theoretical aspects of illocutionary performance that should ideally be included in ESL course book series. Second, it analyzes a collection of seven such course series to assess to what extent they incorporate those theoretical findings. Finally, it considers the weaknesses of present-day textbooks in relation to the teaching of illocutionary acts, thus providing an informed ground for their elaboration and improvement.