This book of the New Testament, like the gospel according to Luke, is dedicated to a certain Theophilus. The dedication declares that the gospel was only the first book of the total work; what now lies before us is the sequel. The author gave no title to this sequel, and its earliest readers may have been somewhat puzzled to know what to call it. Biographies of popular philosophers sometimes went on to include an account of the achievements of the philosopher's followers; and historians occasionally undertook the history of an institution. But there were also biographical accounts of the achievements of famous men which might be called “The Acts of so-and-so”; and perhaps it is for this reason that, since the second century, this work has been known as the acts of the apostles. Nevertheless, the title is not altogether appropriate. Only two apostles, Peter and Paul, are prominent in the story, and only in the second half of the book does one of them (Paul) become the centre of interest. In the first half the real protagonist is the group of early Christians which rapidly grew into the beginnings of a world-wide church.

Greek historians not only wrote a preface to their work as a whole; they often introduced successive books of it by a brief résumé of what had gone before. The beginning of Acts follows this convention and serves to tie the two parts of the work together.