OBJECTIVE: To identify and select common diseases of possible occupational origin, managed through the Spanish National Health System. DESIGN: Cross-sectional study. SETTING: Catalonia (Spain). PARTICIPANTS: Data were collected on people over 15 years of age who were seen for the first time in a primary care clinic or were admitted to a hospital or had an episode of non-occupational sickness absence in catalonia in 2008 or died in this region in 2007. MAIN MEASUREMENTS: A total of 407 diagnostic codes for possible occupationally-related diseases were selected from a modified version of the european union ICD-10 list of diagnostic codes, from which 34 were selected and assessed by an expert panel. RESULTS: The initial 34 diagnoses represented 6.7% of all new outpatient visits, 13.8% of the sickness absence episodes, 13.6% of acute admissions and 15.8% of all annual deaths. Asthma appeared prominently in all four databases. The list was pared down to a final list of 26 four-digit icd-10 codes, that accounted for 3.3% of the first visits, 8.9% of lost work time episodes and 2.7% of acute admissions. CONCLUSIONS: The implementation of a "red flag" into the electronic medical record each time one of these 26 diagnostic codes is entered, could help to improve the reporting of occupational diseases.