BACKGROUND: The functional ability of the patient in chronic diseases reflects the severity of the pathological process and the success of treatment. OBJECTIVE: Evaluation of the functional ability of patients with RA and assessment of the influence of the pathological process on the performance of simple everyday tasks. METHODS: Physical capacity and functional ability were examined using the Groningen activity restriction scale (GARS) and Health Assessment Quesionnaire (HAQ). RESULTS: The authors examined 160 patients with RA (135 women and 25 men), mean age 48.3 +/- 12.13 years and a duration of the disease of 21.32 +/- 15.61 months. The mean value of the functional ability according to GARS was 32.67 +/- 11.61. Women had a poorer score (33.36 +/- 11.91) than men (28.96 +/- 9.44), the difference was however not statistically significant. The mean value of functional ability according to HAQ/FDI of the patients was 1.079 +/- 0.65. Women had a poorer score (1.156 +/- 0.625) than men (0.722 +/- 0.936), the difference being significant (P < 0.01). The authors found a significant correlation (P < 0.001) between HAQ and GARS as well as a significant relationship with parameters assessing the inflammatory activity. In GARS a relationship with the duration of the disease was found (P < 0.05), but not with HAQ. There was no significant relationship between GARS or HAQ with the patients age. In investigations of the restriction of functional ability during common everyday activities it was revealed that the greatest problem of patients is care of feet and nails, climbing stairs and personal hygiene. As to household activities the highest score was recorded for "strenuous house work" (scrubbing floors, cleaning windows and vacuum cleaning), shopping ironing and bedmaking. CONCLUSION: GARS is a reliable practical and simple scale of functional ability of patients with RA which can be used for the accurate description of the severity and for evaluation of the degree of functional ability.