Rheumatic diseases (RDs) are among the most common diseases. In the developed world, they are the leading cause of disability and consume a large amount of health and social resources. Therefore, it is crucial to assess the impact of RDs on the general population in what refers to their prevalence, and repercussion on quality of life and function. However, no nationwide epidemiological studies on RDs have ever been performed in Portugal. With this research project we aim to estimate the prevalence of different RDs in Portugal, as well as to determine the burden of RDs, more specifically their impact on quality of life and functional and work capacity. A cross-sectional study will be performed, using a random sample of the Portuguese population. RDs will be screened through a structured interview, and subjects with a positive screening will be examined by a trained rheumatologist to establish the final diagnosis. The knowledge of the prevalence of RDs will contribute to the development of specific health plans for the current and future management of these diseases.