The study found that the X-chromosome markers included in the Mentype Argus X-8 kit offer the possibility of solving complex kinships cases in which autonomic STR markers do not provide the information needed; however, the study has shown that both linkage and linkage disequilibrium must be taken into consideration when making interpretations in relationship testing based on the tested X-STR markers. This study analyzed a large population sample in order to obtain information about how X-chromosomal markers behave both within a family and at a population level. Regarding frequencies, parameters that describe the tested population and forensic efficiency of the tested loci, the Swedish population sample was found not to deviate from other studied populations; however, one notable observation concerned the population comparison where Swedish X-STR frequencies tended to be more population specific than for autonomic markers. Since DNA results from several X-STR markers are used simultaneously in relationship testing, there is significant risk of observing both linkage and linkage disequilibrium, while linkage disequilibrium, meaning allelic dependency, was observed for all loci within each of the four linkage groups the frequency of recombination between loci in different linkage groups was not always 50 percent, so the assumption of independence did not hold. The descriptions of material and methods address sample and typing, as well as statistical methods. 4 tables, 2 figures, and 20 references