Objective. To know factors related to,job satisfaction among primary care Physicians from the Mexican Social Security Institute. Material and methods. Cross-sectional survey applied to physicians of outpatient visit areas in four Family Medicine Units in Leon, Guanajuato, from February to May 2007. The survey explored six areas. We used 95% confidence intervals and One-Way ANOVA to compare means among clinics and Chi square and OR'95% confidence intervals to compare proportions. Results. One hundred sixty physicians participated (response rate 88.9%), three were excluded. Most physicians were satisfied with their work (86%). Half of the doctors feel satisfied with their economic benefits (48%), non-economic benefits (52%), and those from the collective bargaining agreement (53%), as well as with the labor union (46%) and their actual insurances (45%). Only one third or less of participants refer to receive incentives (31%) or recognitions for their work (33%), were satisfied with the opportunities for training (31%), the economic incentives (29%), or the salary (24%). The satisfaction's means of work, benefits, insurances, labor union and collective bargaining agreement were significantly higher than the means of salary and economic incentives. Satisfaction means were significantly higher in Clinic #53 than in Clinic #51 for job satisfaction and opportunities for training, as well as percentages of response in, institutional support, incentives and recognitions for their work, were higher in Clinic 53 compared to all other clinics; however, it's the smallest clinic in this study. Conclusions. Family doctors find satisfaction in their practice, and factors such as institutional support, recognition and incentives may improve their general job satisfaction.