Acute anterior uveitis (AAU) is the most common form of intraocular inflammation, but its aetiology is still unclear. Fifty percent of AAU patients are HLA-B27-positive, and half of these also have spondyloarthropathies (SpA). Numerous serological studies have shown elevated levels of serum antibodies to various Gram-negative bacteria in HLA-B27-positive AAU and SpA patients. Antigenic similarities between these bacteria and host components (HLA-B27) have already been shown. Still, the mechanism underlying these diseases has not been clarified. Among the Gram-negative bacteria, Helicobacter pylori has not been screened in AAU patients. The purpose of our study was to see if this common human pathogen somehow interferes with AAU. In addition Chlamydia trachomatis, Yersinia enterocolitica 03 and 09, Salmonella sp. and Proteus OX19 were also examined. A total of 60 patients consisting of 4 groups (15 patients with AAU, 15 with SpA, 15 with AAU+SpA and 15 healthy control persons) were examined. A high percentage of the serological results of all investigated bacteria was positive: 80% in the AAU, 93.3% in the SpA and 100% in the AAU+SpA group, while it amounted to 66.7% in the control group (p < 0.05). H. pylori showed the highest percentage of positivity in all 3 patient groups (66.7% in the AAU, 73.3% in the SpA and 80% in the AAU+SpA group). In contrast, 26.7% of the controls were anti-H.-pylori-positive, thus showing a statistically significant difference between the patients and the control group (p < 0.05). HLA-B27/B7-CREG positivity was detected in 53.3% of the AAU, 66.7% of the SpA and 93.3% of the AAU+SpA patients and in none of the controls. Our results suggest that H. pylori might be a candidate participating in the development of AAU and SpA. They also support the theory of genetic (HLA-B27) and exogenous factors (Gram-negative bacteria) as probable background of these diseases.