AbstractGeneral (GVA) and specific (SVA) varietal ability quantify the value of genetic stocks as components for synthetic varieties. Additionally, these parameters can be used to predict the performance of the synthetics. The concept of varietal ability is known for completely allogamous crops. It has not yet been worked out for partial allogamy with a genotype‐dependent degree of cross‐fertilization. We have developed formulae to calculate GVA and SVA referring to generation Syn 1 in this general situation. The concept of varietal ability considers the influence of the components'per seperformance on the resulting synthetic variety. This influence increases with decreasing degree of cross‐fertilization. Thus, our formulae should be of special benefit to partially allogamous crops.The formulae are illustrated by a numerical example taken from our research onVicia fabaL. To estimate the relevant parameters forVicia fabeL., we propose to use two morphological markers (flowers and seed colour) simultane