Occupational diseases affect many people and may have serious social and economic consequences. In 1984, the National Labour Inspection Service established the Register of Occupational Diseases (ROD). The purpose of the central register was to provide information about injury-causing factors and risk groups, etc., changes in risk factors (ongoing monitoring and warning system), and to document the effects of preventive activities. However, we are dealing with several uncertain factors (i.e., whether the number of notified cases is too high or too low), and although the ROD contains a lot of information, it basically represents only notified (suspected) cases, until otherwise proven. Therefore, the utility and reliability of the data in the ROD may be questionable. The National Board of Industrial Injuries and the insurance companies represent recognized and compensated (genuine) cases, but their registers in general contain little information on variables. Thus, it is difficult to obtain exact information of occupational diseases (i.e., the real frequency and causes). What is known, is the number of cases that are notified, recognized and compensated, and the costs. Clearly, the higher the frequency of recognition, the more representative the data in the ROD of the recognized (genuine) cases. Therefore, the course from notification to recognition, and from recognition to compensation was calculated, and, for each step, the importance of skin diseases was considered. Only in the case of skin diseases, was the frequency of recognition high (2/3), and the data in the ROD were considered in more detail, and, where possible, compared with recognized and compensated cases. The various registers concurrently showed that nearly all occupational skin diseases were eczematous in nature (98%), most cases belonged to the younger age group (2/3), women (2/3) predominated over men, and the dominant type of occupational eczema was irritant (2/3). It has not been possible to get further information about exposure sources, occupations and trades from the other registers. However, considering the high frequency of recognition for skin diseases (eczemas), it is likely that the information in the ROD is also to some extent representative of the recognized (genuine) cases. As regards the importance of various disease categories, skin diseases (eczemas) ranked 1st (numerically) among both recognized and compensated cases, and were the most expensive. Therefore preventive activities are mandatory, and because of the high frequency of recognition, the data in the ROD may provide a basis for establishment of the most relevant preventive activities. For other disease categories, the frequency of recognition was low, and the utility and reliability of the data in ROD is in questionable. Therefore, in general, an improvement in the notification system is desirable, but a system that takes into account the many uncertain factors is extremely difficult to set up. Linking of the registers is in progress, and this will be useful during everyday situations.