El Teniente is among the largest underground mines in the world with production of approximately 135,000 tons of copper per day (Baez, 2016). After 112 years of operation, mining is conducted in deeper and more competent rock mass conditions than when the mine was initially opened. The high production rates also require developing a larger number of tunnels in a more efficient way (rapid advance rates at a low cost). For these reasons, El Teniente has defined mine development as a key strategy area for its future, and as such it is continuously looking for technological opportunities to improve safety, efficiency and costs. For many years, ANFO has been the explosive used in this operation. In the last year, emulsion has been extensively tested at El Teniente in horizontal developments to technically quantify their benefits. Trial tests were initially conducted in the Diablo Regimiento sector followed by industrial application in the Pacífico Superior sector. Results show that emulsion has many advantages including a smaller volume of poisonous gases and, therefore, less ventilation time required, and fewer boreholes and greater efficiency in terms of advance per round when compared to ANFO. In this article the fundamentals and statistical analysis of the results derived from field tests at El Teniente are presented and compared.