The aim of the study was to estimate the degree of genetic determination in the decay resistance of Siberian larch (Larix sibirica Ledeb.) wood and its correlation to other wood traits. The wood samples were taken from 25-year-old grafted seed orchard clones with an increment core borer, dried, weighed, and subjected to a laboratory decay test using a modified method based on the standardised EN 113 method. One brown rot fungus, Coniophora puteana (Schum. ex Fr.) Karst., was used as the decaying organism. The advantages of the method were the savings in time, the possibility to study standing trees, and the potential for screening large numbers of samples at reasonable costs. The clonal repeatability was used to estimate the degree of genetic determination. The genetic determination appeared to be stronger for decay resistance than for growth characteristics or heartwood formation, but weaker than for wood density or latewood formation. Decay resistance and the growth characteristics did not correlate.