Summary Haplotype associations of the major histocompatibility complex (MHC) with psoriasis vulgaris (PV) have been demonstrated in different racial or ethnic populations. The objective of this study was to demonstrate the different haplotype associations of the MHC in Chinese patients with psoriasis according to the type of onset and their sex. One hundred and thirty-eight patients with PV and 149 normal control subjects without psoriasis were typed for HLA-A, -B, -C, -DQA1, -DQB1 and -DRB1 by using the PCR with sequence-specific primers. The results showed: (i) HLA-A*26 (26.1% vs. 12.1%, Pc < 1 x 10(-5)), -B*27 (17.03% vs. 1.01%, Pc < 1 x 10(-7)), -Cw*0602 (15.58% vs. 5.03%, Pc < 1 x 10(-2)), -DQA1*0104 (19.93% vs. 9.40%, Pc < 1 x 10(-3)), -DQA1*0201 (22.40% vs. 10.74%, Pc < 1 x 10(-3)), -DQB1*0303 (18.12% vs. 9.73%, Pc < 1 x 10(-7)), and -DRB1*0701/02 (26.09% vs. 9.73%, Pc < 1 x 10(-7)) were significantly increased in PV patients, while HLA-B*57, -DQB1*0201 were slightly increased in PV patients. HLA-Cw*0304 (5.07% vs. 14.43%, Pc < 1 x 10(-3)), -DQA1*0501 (5.79% vs. 14.09%, Pc < 0.05) were found to be negatively associated with PV, but HLA-A*2 (2.54% vs. 6.38%, Pc < 0.5) was decreased in PV patients without statistical significance. (ii) HLA-A*26-B*27 [P < 0.0001, odds ratio (OR) = 48.38], -A*26-Cw*0602 (P < 0.0001, OR = 11.84), -B*27-Cw*0602 (P < 0.0001, OR = undefined), -DRB1*0701/02-B*27 (P < 0.0001, OR = 22.62), -DRB1*0701/02-DQA1*0104 (P < 0.0002, OR = 3.59), -DRB1*0701/02-DQB1*0303 (P < 0.0001, OR = 5.63), -DQA1*0201-DQB1*0303 (P < 0.0002, OR = 7.77), -A*26-B*27-Cw*0602 (P < 0.0004, OR = undefined), -A*26-DRB1*0701/02-DQA1*0201-DQB1*0303 (P < 0.01, OR = undefined) were identified as risk haplotypes for patients with PV in China. (iii) HLA-A*26 -B*27 (P < 0.0001, OR = 58.47), -DQA1*0201-DQB1*0303 (P < 0.0001, OR = 8.62), -DRB1*0701/02 -DQA1*0104 (P < 0.0002, OR = 4.13), -DRB1*0701/02-DQB1*0303 (P < 0.0001, OR = 6.68) and -A*26-DRB1*0701-DQA1*0201 -DQB1*0303 (P < 0.006, OR = undefined) were only significantly associated with type I psoriasis compared with controls, while others showed no differences in either type I or type II psoriasis. (iv) These associated haplotypes with PV were not different by sex, except that the frequency of DRB1*0701/02-DQB1*0303 (P < 0.0001, OR = 10.14) was higher in male patients with psoriasis. To summarize, this study demonstrated a differential association of HLA and identified some special risk haplotypes in Chinese patients with PV compared with other ethnic or racial populations.