Milk from dairy sheep is widely used for high quality cheese production in Spain, as elsewhere. Therefore, genetic improvement of chemical milk composition has to account for the transformation of milk into cheese, because it is a major factor determining yield and quality of the final product. A new analytical method to quantify the Individual Laboratory Cheese Yield (ILCY) of ewe's milk, on the basis of milk quantities compatible with those of the Official Milk Recording (OMR), was elaborated. A description of the method is given. The new variable, ICLY, is then discussed as a selection criterion: recording of new traits, corresponding breeding value estimations, relationships with the dairy traits usually retained for the improvement of milk composition, suitability for updating selection objective (taking into account the specific production system in Churra breed) and possibility of implementation in the ovine milk recording schemes.