This volume contains lectures presented at a meeting on singular perturbations, held in Oberwolfach, Aug. 16 - 27, 1981. In organizing the meeting we have attempted to bring together, and confront with each other, various different types of activities in the field of research in singular perturbations. There were 36 participants (by invitation), from 7 countries, presenting 28 lectures ranging in subject from pure analytic to very applied considerations. The mathematical techniques include classical, functional, non-standard and numerical methods. We wish to thank the authors for the careful presentation of their work.