A human-centric issue that has not been considered in the design of end-user programming environments is whether gender differences exist that are important to the design of these environments. Ignoring this issue would miss the opportunity of enhancing the effectiveness of end-user programmers by incorporating appropriate mechanisms to support gender-associated differences in decision making, learning, and problem solving. This paper takes a first step toward building a foundation for investigating this issue by surveying gender difference literature from five domains with an eye toward possible implications for end-user programming. We present a taxonomy of this literature, and derive a number of specific issues for each element of the taxonomy (stated as hypotheses). This foundation provides a starting point for organized investigations into issues that may be important for making breakthroughs in the effectiveness of end-user programmers.