A genetic map for rat chromosome 1 was constructed using 66 microsatellite markers typed on either or both of two populations derived from inbred Dahl salt-sensitive (S) rats: F2(LEW x S) n = 151, and F2(WKY x S) n = 159. These populations had been raised on a high salt (8% NaCl) diet. Systolic blood pressure and heart weight were found to be genetically linked to two separate regions on rat chromosome 1 in the F2(LEW x S) population. One region was centered around the anonymous SA locus and accounted for 24 mmHg of blood pressure. The other region was 55 cM from the SA locus centered around a cluster of cytochromes P450 loci, and accounted for 30 mmHg of blood pressure. Since blood pressure and heart weight were highly correlated these same regions were also linked to heart weight. These results were cross-specific as linkage of these chromosome 1 regions to blood pressure and heart weight was not observed in several other F2 populations derived by crossing S and other normotensive control strains. This is presumably due to different alleles and/or different genetic backgrounds in the various populations. The SA region of chromosome 1 was found to influence body weight in F2(LEW x S) rats. Combining the present data with our previously published data on the F2(LEW x S) population showed that four separate quantitative trait loci with additive effects accounted for 106 mmHg and 38% of the total variance of blood pressure and for 506 mg and 34% of the total variance of heart wt.