The field study examines the effect of the simulation game Battle Squares modified from Battleships, on the learning of the map reading skill of grid reference determination by Year 7 students. The effect of ability level and sex differences on the acquisition of grid referencing skills were also examined. Modifications produced the major features of the grid system used on Australian Survey Map sheets without substantially altering the characteristics of the game Battleships. Two treatment groups played the simulation game, one group having experienced both a pre test and a post test and the other group only the post test. A third treatment did the pre test and post test without experiencing the simulation game. Students in both treatment groups which experienced the simulation game showed significant gains in the learning of grid referencing skills. Students in upper ability level groups gained significantly better scores on the post test than students in lower ability level groups. Both upper and lower ability level groups showed significant gains. Girls performed significantly better than boys on the post test. Both boys and girls showed significant gains as a result of the simulation game experience. Ability level was a more important moderating variable than sex difference in producing variations in performance on the post test of grid referencing skills.