OBJECTIVES: To determine if the starting time of chemotherapy influences on illness-free survival and general survival in a cohort of Mexican patients with breast cancer METHODS: A prospective study over 5 years was performed on 88 women with breast cancer from the National Medical Centre “La Raza” of the Mexican Institute of Social Security (IMSS) with the following characteristics: stages I-III and positive criteria for adjuvant chemotherapy. The time range for the chemotherapy administration was 0 to 2, 3 and >4 months. The analysis was performed regarding chemotherapy administration time interval using a Kaplan-Meier estimator. The Cox model was adjusted to see the relationships between the global survival and the oestrogen and progesterone hormone receptor variables and HER2/NEU as well as their basal characteristics.  RESULTS: For both IFS and GS there was a significantly statistical difference on the survival distributions related to starting time of chemotherapy which had a higher probability from a range of 0 to 2 months (median GS 59 months median IFS 49 months; p-value<0.001). Regarding general survival, the hormonal receptors for oestrogen, progesterone and HER2/NEU do not influence on the Cox model (p-value=0.137, 0.823, 0.524 respectively); for the Cox model with basal characteristics, age, pathological state and time interval between surgery and chemotherapy influenced significantly on GS (p-value<0.05)  CONCLUSIONS: The probability of survival for IFS and GS improve when chemotherapy is administered within the first 2 months after surgery. Also, there was a greater risk for GS when time interval between surgery and chemotherapy was prolonged. This delay for the starting time of chemotherapy will impact without a doubt in the health systems´ economy, generating more expenses for attention.