Microsatellites have developed into a powerful tool for mapping mammalian genomes and first reports about their use in plants have been published. A database search of 228 barley sequences from GenBank and EMBL was made to determine which simple sequence repeat (SSR) motif prevails in barley. Nearly all types of SSRs were found. The (A)n and (T)n SSRs occurred more often than (C)n and (G)n for n > or = 10. Among the dinucleotide repeats, the (CG)n SSRs occurred least often. Trinucleotide repeats did not occur with n > 7 and there is no correlation between the GC content in the trinucleotide motifs and the number of observed SSRs. Analysing 15 different microsatellites with 11 barleys yielded 2.1 alleles per microsatellite. Sequencing 25 putative microsatellites showed that the resolution capacity of high-quality agarose gels was sufficient to determine differences of only three base pairs. Five microsatellites were mapped on three different chromosomes of a barley RFLP map.