Low back pain (LBP) is a common medical problem. Interaction between genetic and environmental factors predisposes individuals to LBP even at an early age. Inflammatory back pain or spondylarthropathies include ankylosing spondylitis (AS), psoriatic arthritis (PSA), reactive arthritis enteropathic and undifferentiated arthropathies. Angiotensin-converting enzyme (ACE) plays an important role in circulatory homeostasis, physiology of vasculature and inflammation. The insertion-deletion (I/D) polymorphism of the ACE gene has been shown to determine the plasma and tissue levels of ACE especially in the synovial fluid. The aim of this study was to investigate an association between ACE gene I/D polymorphism and inflammatory back pain (spondylarthropathies) secondary to ankylosing spondylitis (AS), psoriatic arthritis, inflammatory bowel disease and undifferentiated spondylarthropathies. The prevalence of ACE gene I/D polymorphism genotypes was determined in 63 patients with inflammatory back pain by polymerase chain reaction (PCR) and compared with that in 111 healthy controls. Of the 63 patients studied, 45 (71.4%) were with AS, 13 (20.6%) were with PSA, 4 (6.3%) were with reactive arthropathy and 1 (1.6%) manifested undifferentiated arthropathy. There were 43 males and 20 females. Mean age of patients was 39.0+/-11.36 years, age at onset of spondylarthropathy was 27.7+/-7.49 years and disease duration was 10.3+/-7.74 months. The controls were selected to match with the patients group in terms of gender ratio, age and ethnicity. The ACE gene polymorphism showed an overall significant difference between patients and controls (p=0.050). When the ID and II genotype frequency was combined and compared with that for DD genotype amongst patient and control groups, a considerably higher incidence was detected for ID and II genotypes than the DD genotype in spondylarthropathy patients compared to that in the controls (p=0.036). This study showed a significant association of the I-allele of ACE gene I/D polymorphism with spondylarthropathy in Kuwaiti Arabs.