The effect of relative humidity, atmospheric pressure, cloudcover, outside temperature, wind velocity and an overall weather index on Ritchie articular index (RAI) and pain registered on visual analogue scale (VAS) have been studied in active rheumatoid arthritis cases. Nineteen such cases were studied prospectively during the hospitalization for an exacerbation of the disease in the winter of 1981-82. Sixty-nine per cent of the patients were found to be sensitive, according to the RAI and VAS scores, to a weather indicator and 16% were not sensitive at all. To be weather sensitive, patients had to have at least one significantly positive correlation. The weather indicators most often positively associated with rheumatic symptoms were relative humidity, outdoor temperature, cloudiness and the overall weather index. There was no absolute correlation between the subjective claim to be weather sensitive and the objective correlations with weather parameters and joint pain.