Breeding groups, subdivisions of a breeding population composed of superior individuals, are equivalent to inbred lines in crop breeding. Breeding groups are being used to control inbreeding in a breeding population and to effectively achieve maximum genetic gains in some tree improvement programs of the United States. The use of breeding groups does not change the breeding values of the subdivided populations. The genetic variance of breeding values within a breeding group, however, will be increased depending on the degree of inbreeding in each group. Such variance change will increase the total genetic variation and offer a better chance for selection of desirable genotypes for successive generations of breeding groups. Furthermore, breeding groups will add only paper work to keep records separate for a tree improvement program manager, but they can be easily implemented in a forest tree improvement program without extra field work.