There are two phases of somatic muscle formation in Drosophila. During embryonic development, one phase of myogenesis generates larval muscle elements that mediate the relatively simple behavioural repertoire of the larva. During pupal metamorphosis, a diverse pattern of muscle fibres are assembled, and these facilitate the more elaborate behavioural patterns of the adult fly. In this review, we discuss the current status of understanding of the cellular, genetic, and molecular mechanisms of pattern formation during the second phase, imaginal muscle development. We briefly compare aspects of embryonic and adult myogenesis in Drosophila and muscle development in vertebrates and highlight conserved themes and disparities between these diverse myogenic programmes.