The erythrocyte diameter curve of Price-Jones exhibits symmetrical, normal distribution. In contrast, the volume distribution curve of erythrocytes shows an asymmetrical course with some skewness to the right, which with different haematological diseases may vary. With respect to differential diagnosis as well as to therapy it is of importance to have available an objective means of comparing curves with different shapes. We therefore developed a mathematical determination of the volume distribution curves, which derived from the overlapping of two Gaussian normal distribution curves. Volume distribution curves of erythrocytes were determined with an electronic particle counter (Coulter counter) in 271 healthy and haematologically affected children as well as in 3 adults. With only one exception all volume distribution curves of erythrocytes could be fitted using computer analysis and the constants m1, m2, s1 and s2 were calculated. Characterisation of the curves with only these 4 constants allows a simple qualitative as well as quantitative comparison of different volume distribution curves.