The haematology analysers Coulter(R) GEN.S(TM) and LH(TM) give a set of data--'positional parameters'--which define each WBC population by mean of index values, the mean and the standard deviation (SD) of volume, conductivity and scatter, used to identify the WBC populations. These parameters were analysed in patients investigated for suspicion of malaria, in order to show a difference between malaria negative and malaria positive patients and to use it for malaria detection. The six parameters exhibiting a significant difference between the two groups were submitted to a ROC analysis, which showed both sensitivity >90% and specificity >60% for two parameters, lymphocyte and monocyte SDs of volumes. A discriminator combining the two parameters showed a sensitivity of 96.9% and a specificity of 82.5%. The cut off of the discriminative value was calculated. Because of the good stability and reproducibility of the parameters selected, the test can be used in order to detect patients having a high probability to be malaria positive and to pay particular attention to these blood smears. For more extensive diagnostic use, a standard control procedure of the positional parameters should be introduced.