Safety literature confirms that incentives such as money or sunglasses seem to improve safety conditions over the short run. However, no studies could be found which tested the effect of incentives on fall protection for a period longer than a few days. In our research we found that after 6 months, the use of non-material incentives significantly improved on-time delivery and completion rates of a special inspection form (both p <.005). In addition, a questionnaire with embedded critical questions showed that even though workers said that they preferred material incentives, we conclude that their behavior was changed by the treatment (incentives). We further conclude that the use of natural reinforcers seems to influence worker behaviors and perception of management's commitment to safety over the long run, even though workers still say that they prefer tangible rewards. Future work should replicate these findings and explore why workers respond to natural incentives but express a preference for material incentives.