OBJECTIVE To evaluate whether there is a relationship between HLA-A, -B, -Cw, and -DRB1 alleles and developing nasal polyposis (NP). STUDY DESIGN Data from 66 patients with NP were compared with data from 100 healthy randomly selected controls. Asthma, ASA (acetylsalicylic acid) triad, polyp score, and previous sinonasal surgery were also recorded. SUBJECTS AND METHODS Genotyping of the HLA-A, -B, -Cw, and -DRB1 alleles were performed with polymerase chain reaction (PCR) with the sequence-specific primer (SSP) method. Data were analyzed by using a Pearson chi(2) test. RESULTS The HLA-B*07 and -Cw*12 alleles were found to be significantly higher in the NP patients compared with the control group, whereas the HLA-B*57 and HLA-Cw*04 alleles were significantly lower (P < 0.05). The HLA-A*24, HLA-Cw*12, and HLA-DRB1*04 alleles were determined to be significantly higher in the NP patients with asthma and ASA triad (P < 0.05). CONCLUSIONS Our results show that some of the HLA alleles seem to be associated with the genetic susceptibility to develop NP in the Turkish population.