OBJECTIVES: It is hypothesised that socio-economic factors play a key role in determining treatment patterns. This study investigated the impact of employment and gender on asthma treatment patterns in 2526 patients in the US, Germany and Spain. METHODS: The data were drawn from the Adelphi Disease Specific Programme (DSP) in asthma, a cross-sectional study of consulting patients undertaken in 2007. Data were collected by doctors who were asked to include the next 6 patients consulting for asthma from a specified start date. Key factors analysed were gender and employment status (skilled, unskilled, unemployed). Chi-square and Fisher's exact tests were used to test for differences. RESULTS: There was a significant relationship between employment status and patients' level of knowledge about their condition. Skilled workers had a higher level of knowledge as compared to unskilled workers (US: 37.3% vs. 18.3%, p<0.001; Germany: 35.3% vs. 22.5%, p<0.05; Spain: 26.7% vs. 15.9%, p=0.06). Skilled workers also had more involvement in treatment decisions (US: 50.0% vs. 32.3%, p<0.001; Germany: 35.3% vs. 18.8%, p<0.001; Spain: 21.6% vs. 13.4%, p=0.1) and were rated more compliant than unskilled workers (US: 56.3% vs. 37.1%, p<0.001; Germany: 45.3% vs. 28.4%, p<0.01; Spain: 35.1% vs. 23.2%, p=0.06). There were no significant differences between genders other than Spain where significantly more men had a higher level of knowledge about their condition (24.5% vs. 17.2%, p<0.01) and more involvement in their treatment (20.9% vs. 14.5%, p<0.05). In all countries a significant positive correlation was found between level of involvement and compliance with treatment (p<0.01). CONCLUSION: There are significant differences in knowledge, involvement and compliance between socio-economic groups in the US, Germany and Spain. The significant correlation between level of involvement and compliance may indicate that if physicians made particular efforts with lower socio-economic groups in treatment decisions compliance levels would improve.