Editorial - the biology and conservation of New World primates, H.O. Box and H.M. Buchanan-Smith; mate preferences of wild muriqui monkeys ("Brachyteles arachnoides") - reproductive and social correlates, K.B. Strier; conservation of neotropical primates - threatened species and an analysis of primate diversity by country and region, A.B. Rylands et al; geographic distribution of the golden-headed lion tamarin, "Leontropithecus chrysomelas" - implications for its management and conservation, L.P. de S. Pinto and A.B. Rylands; uncertain conservation status of squirrel monkeys in Costa Rica, "Saimiri oerstedi oerstedi" and "Saimiri oerstedi citrinellus", S. Boinski and L. Sirot; feeding behaviour and predation of a bat by "Saimiri sciureus" in a semi-natural Amazonian environment, L.L. Souza et al; effects of habitat quality and hunting pressure on arboreal folivore densities in neotropical forests - a case study of howler monkeys ("Alouatta" spp.), C.A. Peres; the ecology, biogeography and conservation of the uakaris, "Cacajao" (Pitheciinae), A.A. Barnett and D. Brandon-Jones; experimental field study of spatial memory and learning in wild capuchin monkeys ("Cebus capucinus"), P.A. Garber and L.M. Paciulli; can spider monkeys ("Ateles geoffroyi") discriminate vocalizations of familiar individuals and strangers?, P. Teixidor and R.W. Byrne; social memory in saddle-back tamarins ("Saguinus fuscicollis"), G. Epple and H. Niblick; tamarin mixed-species groups - an evaluation of a combined captive and field approach, H.M. Buchanan-Smith and S.M. Hardie; the relationship between body size and mixed-species troops of tamarins ("Saguinus" spp.), E.W. Heymann; foraging strategies among male and female marmosets and tamarins (Callitrichidae) - new perspectives in an underexplored area, H.O. Box; autonomic balance in "Saimiri sciureus" and "Callicebus moloch" - relation to life-style, S.P. Mendoza and W.A. Mason.