We investigated the association of human leukocyte antigens (HLA) class II alleles and haplotypes with the pathogenesis of acute chest syndrome (ACS) in 186 sickle cell anemia (SCA) patients, of whom 58 had documented ACS (new pulmonary infiltrate, fever, and other associated clinical events) and 128 with a negative history of ACS, serving as controls. HLA DRB1* and -DQB1* genotyping was performed by polymerase chain reaction-sequence-specific priming. Of the DRB1* and DQB1* alleles analyzed, only DRB1*130101 (Pc < 0.001) was positively associated with ACS. DRB1*130101-DQB1*060101 haplotype was more prevalent among ACS patients (P = 0.018), thus conferring disease susceptibility. Specific HLA alleles and haplotypes may influence ACS risk in SCA patients, and specific HLA genotypes may be useful markers for identifying high-risk SCA ACS patients.