Uncertainty of returns from marketing is an extremely important factor affecting the diffusion of a wide range of genetically modified (GM) crops worldwide. Biotech companies face complicated choices in making decisions about whether to enter agricultural markets in different countries with their agricultural products. In this paper, we model these choices as a real option problem of entry decision solved at a micro-level by individual firms. The model is aggregated in order to reflect the heterogeneity of different genetic events, as well as different markets, in terms of their profitability. The solution to the model produces distributions of entry probabilities as functions of the functional forms (and parameter values) that govern the evolution of stochastic returns from marketing. These proportions are then compared to the actual data on incidences of biotech firms entering foreign markets with different GM crops, and conclusions about the distribution of their patent values, evolution of returns, and efficiency of local IPR protection are drawn.