Abstract
The authors, together with other co-workers, have already estimated the average effective population size of the Kiso horses in a period from 1955 to 1961 as about 90 per year from the number of male parents and the variability in progeny number of male parents. In the present work the average effective size of this horse population was estimated from the random fluctuation of the frequencies of genes controlling polymorphism for coat-colors and red blood cell antigens by using a method developed by one of the authors (Nozawa 1963). The value obtained, 88.51 (57.78-152.59) per year, was considered to agree with the estimate from the breeding record.
