Full blood counts and some serum biochemistry were carried out on 349 male and 22 female apparently healthy Papua New Guinea subjects, most of whom were highlanders. In males, RBC, Hb, PCV, MCH, MCHC, serum albumin, ferritin, iron, per cent transferrin saturation and folate means were significantly lower than the Australian normal means; WBC and MCV means were similar to Australian values; and eosinophil and reticulocyte counts and serum transferrin and vitamin B12 means were higher than Australian means. In females, WBC, RBC, Hb, PCV, MCV, MHC, MCHC and serum ferritin means were lower than Australian means; eosinophil counts, serum iron, per cent transferrin saturation, and folate means were similar to Australian means; and serum transferrin and B12 means were higher than the Australian means. Hepatomegaly and mild splenomegaly were common. beta-Thalassemia was present in three subjects two of whom were from Simbu Province.