The growth of four variables of the ischium was analysed by polynomial regression in order to evaluate its significance and its capacity for age and sex determination during and after growth. The material used was 327 specimens ranging from birth to 97 years of age from four documented west European collections. The growth curves were calculated for ischium length and three new variables of the acetabular surface (horizontal diameter of ischium acetabular surface, vertical diameter of ischium acetabular surface and ischium acetabular index). All curves, except those of the female series of vertical diameter of ischium acetabular surface and its index, showed a lineal growth corresponding to vertical variables. All variables studied, except the ischium acetabular index, can be used variables for adult sexual discrimination. Furthermore, ischium length and the horizontal and vertical diameters of the acetabular surface can be useful for sub-adult age determination in archaeological samples, as well as in forensic samples. However, the ischium length is the best variable, as it can be applied to all the growth ages.