What determines companies to file patents? To answer this question we present a systematic review, in which 22 empirical studies published in scientific periodicals were selected. Based on the descriptive analysis of these studies, a framework is proposed that brings together a set of explanatory variables that influence the propensity to patent in internal and external factors. The cumulative results of the reviewed articles suggest a positive correlation of firm size and R & D with the propensity to patent. A unanimous result among the articles is that the Industrial Sector in which the company is inserted has a significant influence on the propensity to patent. Regarding the variables Age, Collaboration Network and Competition, the results of the research were divergent, indicating a positive, negative or non-significant relationship. However, these determinants are still poorly understood due to the divergence of the research results.