Plans to improve the milk production ability of the Criollo in Bolivia are outlined. The background problems are stated, and experiments to improve by crossbreeding are described. The Criollo improvement project which makes use of the purebred Criollo was planned in two stages. The first was the attempt to measure the performance of Criollo cows purchased from commercial herds, and milked without their calves. The second stage was the comparison of performance with the results of the crossbred trial. The intentions and plans to progeny test the Criollo bulls are summarized and the hopes of producing bulls for sale and use on temperate breeds of cow are described. The problems encountered in the project are stated, and the results are viewed in the context of work with Criollo in other countries.