Gene‐centromere distances can be estimated (i) by determining postreduction frequencies by means of ovarian teratomas and (ii) by analysis of genetic linkage between a gene locus and a structural chromosome polymorphism near the centromere. The two methods are compared under complete interference. It is shown that the teratoma method is at least twice as efficient as the recombination method. Two estimates of the map distance for a combination of both data types are derive