INTRODUCTION. - Yield gap analysis is a powerful method to explore gap's breadth between potential yields, attainable and those realized in farmers' fields, identifying constraints and opportunities for yield increase. Understanding and ranking the main causes of yield gaps is essential to provide feedback to farmers and extension agents, contributing to reduce both yield gap and yield variability between farms (Lobell et al., 2009). This paper aims to quantify yield gaps in greenhouse tomato crops in the south region of Uruguay and assess opportunities for increasing tomato production by modifying those factors defining potential yield or 'yield defining factors' (Van Ittersum and Rabbinge, 1997).