Pulmonary hypertension syndrome (PHS), also referred to as ascites syndrome, isa growth-related disorder of chickens frequently observed in fast-growingbroilers with insufficient pulmonary vascular capacity at low temperature and/orat high altitude. A cross between two genetically different broiler dam linesthat originated from the White Plymouth Rock breed was used to produce athree-generation population. This population was used for the detection andlocalization of quantitative trait loci (QTL) affecting PHS-related traits. Tenfull-sib families consisting of 456 G2 birds were typed with 420 microsatellitemarkers covering 24 autosomal chromosomes. Phenotypic observations werecollected on 4202 G3 birds and a full-sib across family regression intervalmapping approach was used to identify QTL. There was statistical evidence forQTL on chicken chromosome 2 (GGA2), GGA4 and GGA6. Suggestive QTL were found onchromosomes 5, 8, 10, 27 and 28. The most significant QTL were located on GGA2for right and total ventricular weight as percentage of body weight (%RV and %TVrespectively). A related trait, the ratio of right ventricular weight aspercentage to total ventricular weight (RATIO), reached the suggestive thresholdon this chromosome. All three QTL effects identified on GGA2 had their maximumtest statistic in the region flanked by markers MCW0185 and MCW0245 (335-421cM).