There is an inherent difficulty in converting gravity data into geologic information because the problems have to be solved indirectly. This difficulty has given rise to an intellectual gap between people who interpret gravity data and those who apply the results. With a view to bridging this gap, a check list of variables important to the correlation of gravity and geology is offered. This should help the non-specialist to obtain a better idea of where gravity will give him useful information. Remarks are made on the role each variable plays in the interpretation process and on the accuracy with which each may be used in computations. The effect of target depth on residual and derivative interpretation methods is examined. Examples are given showing the extent to which information about geologic structures can be got from gravity.