OBJECTIVE: To determine whether physicians document office visits differently when they know their patients have easy, online access to visit notes. PATIENTS AND METHODS: We conducted a natural experiment with a pre-post design and a nonrandomized control group. The setting was a multispecialty group practice in Minnesota. We reviewed a total of 400 visit notes: 100 each for patients seen in a rheumatology department (intervention group) and a pulmonary medicine department (control group) from July 1 to August 30, 2005, before online access to notes, and 100 each for patients seen in these 2 departments 1 year later, from July 1 to August 30, 2006, when only rheumatology patients had online access to visit notes. We measured changes in visit note content related to 9 hypotheses for increased patient understanding and 5 for decreased frank or judgmental language. RESULTS: Changes occurred for 2 of the 9 hypotheses related to patient understanding, both in an unpredicted direction. The proportion of acronyms or abbreviations increased more in the notes of rheumatologists than of pulmonologists (0.6% vs 0.1%; P=.01), whereas the proportion of anatomy understood decreased more in the notes of rheumatologists than of pulmonologists (-5.9% vs -0.8%; P=.02). One change (of 5 possible) occurred related to the use of frank or judgmental terms. Mentions of mental health status decreased in rheumatology notes and increased in pulmonology notes (-8% vs 7%; P=.02). CONCLUSION: Dictation patterns appear relatively stable over time with or without online patient access to visit notes.