Objective. To estimate the impact of occupational diseases in Spa-in in terms of incidence and prevalence and to compare them with the notifications actually made. Design. Data of incidence and prevalence were obtained from studies carried out in Spain and in other countries. These studies were mostly based on epidemiological investigations, occupational diseases monitoring systems and surveys with representative samples of workers. Participants. Data of incidence and prevalence were applied to the whole of working population in Spain in 2006. Setting. Spain, 2006. Main measurements. Incidence and prevalence of occupational diseases and illness (including musculoskeletal, skin, respiratory and mental diseases and malignant cancers). Results. It is estimated that a mean of 87 856 incident cases of occupational diseases occurred in Spain in 2006, most of them musculoskeletal diseases (30 757 estimated incident cases) and skin diseases (12 481 cases). Moreover, according to our estimations, 9153 respiratory diseases, 8205 cases of mental illness and 6082 malignant cancers related to different occupational exposures were diagnosed in Spain in 2006. A total of 999 591 male workers and 1007 862 female workers suffered some disease or illness related to their working conditions, the most common being musculoskeletal and mental diseases. Conclusions. Occupational diseases impact could be quite over what it is showed in the official occupational diseases registry in Spain. It is necessary to give visibility to this problem to provide adequate care and prevention of occupational diseases in the population.