The extent and structure of genetic variation in 720 individuals representing 36 populations of wild barley, Hordeum spontaneum, from Central Asia (Turkmenistan) were determined using starch gel electrophoresis of eight water soluble leaf proteins encoded by 13 loci. The populations were grouped into seven ecogeographic regions. The study found: (a) a similar amount of within population genetic diversity (He = 0.106), but lower total genetic diversity (HT = 0.166) to that reported for Middle East populations of H. spontaneum; (b) of the total genetic diversity, 61% was attributable to variation within populations, 27% between populations of a region, and 12% among regions; (c) of the 42 alleles found, 11 were ubiquitous, 22 were widespread and common, three local and common and seven local and rare; (d) there was a poor correlation between population genetic and geographic distances; and (e) the frequencies of only a few alleles correlated significantly with climatic or geographic parameters. The extent and structure of genetic variation of Turkmenian populations, which represent the Central Asian part of the species' range, were significantly different in some important aspects from Middle Eastern and eastern Mediterranean populations. The mosaic pattern of genetic variation found in wild barley in the Middle East is less pronounced in populations from Central Asia where there is less genetic differentiation among populations and regions, and more ubiquitous or common and fewer localized alleles.