A detailed linkage map of Helianthus annuus was constructed based on segregation at 234 RFLP loci, detected by 213 probes, in an F2 population of 289 individuals (derived from a cross between the inbred lines HA89 and ZENB8). The genetic markers covered 1380 centiMorgans (cM) of the sunflower genome and were aranged in 17 linkage groups, corresponding to the haploid number of chromosomes in this species. One locus was found to be unlinked. Although the average interval size was 5.9 cM, there were a number of regions larger than 20 cM that were devoid of markers. Genotypic classes at 23 loci deviated significantly from the expected ratios (1∶2∶1 or 3∶1), all showing a reduction in the ZENB8 homozygous class. The majority of these loci were found to map to four regions on linkage groups G, L and P.