Pii: S0168-9525(98)01573-x

410 Copyright © 1998 Elsevier Science Ltd. All rights reserved. 0168-9525/98/$19.00 PII: S0168-9525(98)01573-X The elimination of unwanted cells by programmed cell death is an important developmental and homeostatic process in multicellular organisms, including the nematode Caenorhabditis elegans1. During the development of the C. elegans hermaphrodite, 1090 cells are generated, of which 131 undergo programmed cell death2–4 (Fig. 1). Genetic analyses of C. elegans have identified genes that function in programmed cell death, ordered these genes in a genetic pathway and led to the finding that similar genes control programmed cell death in other organisms, including mammals. In this review, we concentrate on the genetic and developmental studies of C. elegans that have resulted in these discoveries. We mention only briefly molecular biological and biochemical studies of programmed cell death, which have been described in a number of recent reviews5–8. We focus primarily on mechanisms of cell killing and, for this reason, do not discuss in detail the engulfment or degradation of cell corpses.