Two methods of estimating linkage test power are proposed. The first method is based on the maximum likelihood (ML) estimate of the recombination fraction and is intended for use with a likelihood ratio test (LRT) in the form of a chi 2 or lod score. The power is estimated through a noncentral chi 2 distribution with a specially chosen noncentrality parameter. The second method uses the LRT constructed for a simple alternative hypothesis regarding the recombination fraction value. The approximate distribution of this test and a method of estimating its power is proposed. Using simulated pedigree data, the power estimates for these two methods were shown to be satisfactory. Comparisons among these two methods and the computer simulation approach of Boehnke  are performed.