OBJECTIVES: To identify the association of socio-demographic, resource use, and adverse events variables with adherence to measure the return on investment of a patient education service for colorectal cancer patients taking capecitabine. METHODS: This was a prospective intervention of government patients in the country of Mexico of any age, with colorectal cancer and capecitabine treatment. The intervention group had access to a hot line, booklets, nutritional and psychological support; control group patients did not. A structured ad-hoc questionnaire applied the Morisky-Green Test to determine adherence to therapy via follow up phone calls. Associations between variables and adherence between intervention group and controls were assessed using chi-square test. Emergency rooms (ER) visits were the economic indicator to establish cost differences between groups. Power analysis was conducted using PS Power and Sample Size Calculations version 3.0, January 2009.  RESULTS: A total of 220 patients were included in this study (mean age 58.4[26 to 89] years), 121 intervention patients (48 responded to first call; 70% adherence) and 99 control patients (30 responded to first call; 57% adherence). If the true odds ratio for adherence in intervention relative to control is 1.86, a power analysis projects statistical significance with 290 intervention patients and 181 controls to reject the null hypothesis with a probability (power) of 0.8. The reason for non-adherence “Does not know administration regime” did show statistical significance (p=0.019) between the intervention (10% n=2) and control group (47% n=7). For ER visits related to adverse events, the control group rate was 13.33% (n=4) vs. 2.32% (n=1) in the intervention group (p=0.067). The cost for ER/day is $Mex 1,144.44 (USD 86.82). CONCLUSIONS: These preliminary results indicate that patients who receive intervention services may have improved adherence to medication and therefore fewer ER visits and costs. Continued enrollment will be able to determine true significance.