Departme nts o f Vete rinary Path ol ogy, Veter inar y Ph ysio logy and Phar maco logy, a nd Veterinary Publ ic Hea lth, Co llege of Vete rina ry Medi cine, Texa s A & M Un ivers ity, Co llege Sta tion , Tex.Abstract. T he toxic effec ts of Nerium oleander were eva luated in cap uchi n mon keys ( Ce!JlI.\' apella) by exa mi na tion of clin ica l s igns, hemat ol ogic and serum chem ical va lues, a nd gross a nd micro scopic lesion s. Dr ied and gro und o lea nder lea ves were given a t intervals of 48 h in doses o f 30, 7.5, an d 3 rug/kg bod y weight. T he cum ula tive lethal dose ranged from 30 to 60 rng/kg bod y weig ht in mon keys that were given do ses of 30 and 7.5 mg/kg bod y weight. M on keys that received do ses of 3 mg/kg bod y we ight (tota l cumula tive dose : 60 mg/kg) sur vived. C linica l signs were vom iting, sa liva tio n, po lyuria , bradycard ia, vagina l hem orrh a ge, abortio n, a norex ia, co nst ipa tio n, loss of bo dy weight, na rcosis, rest lessness, weakness, a nd sha llow a nd ra pid respira tions. C ha nges in blood va lues were leu kocytosis ; neu tr oph ilia ; increased potassium, gluta mic-oxa lacet ic tra nsa minase, glutamic-pyruvic transaminase, blo od urea n itrogen a nd a-g lob ulins ; reticulecyto pe nia ; a nd decreased ca lciu m, gluco se, to ta l serum protein, a lbum in, y-g lob ulin levels a nd a lbumin-globulin ra tio s. Hem orrhages, degen erat io n, or necrosis, or a ll of these, were ob served in the hea rt , gastro intestina l tract , skeleta l mu scles, ovaries, a d rena l gla nd s, liver, kidn eys, a nd pan creas. T he o rga n we ights of th e pancrea s were significa ntly redu ced . Adrena l weig hts were significa ntly increased in mo nke ys that received the highest do se level.