The six papers in this special issue of "Computers and Education" honoring Professor David H. Jonassen are diverse in nature. They also reflect differing interpretations of the implications of Jonassen's work for research and development focused on instructional models and the factors influencing instruction as well as the directions for future research on learning technologies. Nonetheless, the papers all acknowledge the enormous impact Jonassen has had on generations of educational technology researchers as well as the growing influence his work is having on the teaching and learning practices of teachers and trainers across all sectors of education and training.