Complete medical examinations were performed on 20 wild Decken's sifaka (Propithecus verreauxi deckeni) and 20 wild red-fronted brown lemurs (Eulemur fulvus rufus) from western Madagascar. Each animal received a complete physical examination, and weight, body temperature, heart rate, and respiratory rate were recorded and ectoparasites collected. Blood samples were collected for complete blood cell count, differential white blood cell count, hemoparasite examination, serum biochemical profile, fat-soluble vitamin analysis, trace mineral analysis, and toxoplasmosis and viral serology. Fecal samples were collected for bacterial culture and endoparasite examination. Significant differences exist between the species for serum chemistry values for creatine phosphokinase, glucose, total protein, albumin, globulin, blood urea nitrogen, creatinine, phosphorus, potassium, and chloride; for fat-soluble vitamins 25-hydroxycholecalciferol, retinol, retinyl palmitate, γ-tocopherol, α-tocopherol, and lutein zeaxanthin; and serum copper. Parasites detected include Lemurostrongylus spp., Lemuricola spp., Trichurus spp., and ectoparasites Haemaphysalis lemuris, Psoroptes, and mites identified to the family Laelapidae. Enteric bacterial flora included Escherichia coli, Citrobacter ssp., Enterococcus faecalis, Bacillus cereus, Klebsiella ozaenae, Acinetobacter lwofii, and Enterobacter amnigenus.