The haptoglobin phenotypes of Sudanese patients with complicated and uncomplicated falciparum malaria, and those of uninfected randomly selected individuals, were determined by electrophoresis of sera on polyacrylamide gels followed by benzidine staining of the gels. Among 273 malaria patients, the proportions with haptoglobin phenotypes (1-1), (2-1) and (2-2) were 60.8%, 29.7% and 9.5%, respectively, and in 72 cerebral malaria patients the proportions were 63.9%, 29.2%, and 6.9%. The distribution among 208 control individuals was 26.0%, 55.8% and 18.3%, respectively. The difference between patients and controls was highly significant (P < 0.001). The distribution of the different haptoglobin phenotypes among the randomly selected group of 208 Sudanese individuals was comparable to that in many other populations. The results suggests that the haptoglobin phenotype (1-1) is associated with susceptibility to falciparum malaria and the development of severe complications; alternatively, the other phenotypes may confer resistance.