Abbreviation use is a preventable cause of medication errors. The objective of this study was to test whether computerized alerts designed to reduce medication abbreviations and embedded within an electronic progress note program could reduce these abbreviations in the non-computer-assisted handwritten notes of physicians. Fifty-nine physicians were randomized to one of three groups: a forced correction alert group; an auto-correction alert group; or a group that received no alerts. Over time, physicians in all groups significantly reduced their use of these abbreviations in their handwritten notes. Physicians exposed to the forced correction alert showed the greatest reductions in use when compared to controls (p=0.02) and the auto-correction alert group (p=0.0005). Knowledge of unapproved abbreviations was measured before and after the intervention and did not improve (p=0.81). This work demonstrates the effects that alert systems can have on physician behavior in a non-computerized environment and in the absence of knowledge.