Procalcitonin, the precursor of calcitonin, is elevated in patients with sepsis and infection (base-line values <0.1 ng/ml). We determined PCT in 38 hospitalised patients with suspected malaria. All of them had signs of infection and had recently returned from Africa. Plasmodium vivax was proven in 15, Plasmodium falciparum in one and an infection with both species was found in another case (n = 17). PCT was determined on admission and the days thereafter. In one patient PCT was determined every 4 hours on the first day. The maxima of the PCT concentration on day 0 and 1 were 5.3 ng/ml with proven Malaria and 0.43 ng/ml without. At the following days we found a decrease to normal values (<0.5 ng/ml) which correlated with the general condition of the patient. At a cut-off point of 2 ng/ml we found a sensitivity of 52%, positive predictive value of 74%, specificity of 86%, negative predictive value of 71%. procalcitonin, malaria