Objective: To investigate whether health insurance affiliation and socioeconomic deprivation is associated with overall cause survival from gastric cancer in a middle-income country. Methods: All patients resident in the Bucaramanga metropolitan area (Colombia) diagnosed with gastric cancer between 2003 and 2009 (n= 1039), identified in the population-based cancer registry, were followed for vital status until 31/12/2013. Kaplan-Meier models provided crude survival estimates by health insurance regime (HIR) and social stratum (SS). Multivariate Cox-proportional hazard models adjusting HIR and SS for sex, age and tumor grade, were performed. Results: Overall 1 and 5 year survival proportions were 32.4% and 11.0%, respectively, varying from 49.3% and 15.8% for patients affiliated to the most generous HIR to 12.9% and 5.3% for unaffiliated patients, and from 41.4% and 20.7% for patients in the highest SS, versus 27.1% and 7.4% for the lowest SS. The multivariate analyses showed type of HIR as well as SS to remain independently associated with survival, with an 11% improvement in survival for each increase in SS subgroup (HR 0.89 (95% CI 0.83; 0.96), and with worse survival in the subsidized (least generous) HIR and unaffiliated patients compared to the contributory HIR (HR subsidized 1.20 (95% CI 1.00; 1.43) and HR not affiliated 2.03 (95% CI 1.48; 2.78)). Of the non-affiliated patients, 60% had died at the time of diagnosis, versus 4-14% of affiliated patients (p<. 0.0005). Conclusions: Despite the 'universal' health insurance system, large socioeconomic differences in gastric cancer survival exist in Colombia. Both social stratum and access to effective diagnostic and curative care strongly influence survival.