BACKGROUND: Home blood pressure measurement (HBPM) is recommended for the diagnosis and follow-up of hypertensive patients. While measurement protocols emphasize a rest period before taking the measurement, this directive has not been supported by any specific study to date. This analysis aimed to determine whether the respect or nonrespect of rest before HBPM could introduce a difference between daytime ambulatory blood pressure measurement (ABPM) and HBPM; whether this rest is observed "in real life" among educated hypertensive patients. METHODS: In this open, prospective study we compared HBPM, with and without rest, and ABPM among 52 office/clinically controlled hypertensive patients. HBPM was performed during 3 days (French HAS instructions); 24-hour ABPM was performed within 3 days of HBPM. All patients who regularly performed HBPM before the study were asked how they practiced HBPM in real life. RESULTS: There was a differential impact of rest on differences observed in daytime ABPM and HBPM. Systolic HBPM decreased with rest, while diastolic HBPM did not significantly increase. HBPM systolic BP (SBP) without rest was not significantly different from daytime ABPM SBP (P = 0.27). HBPM SBP without rest was lower than daytime and 24-hour systolic ABPM. Diastolic HBPM after rest was not significantly different from daytime diastolic ABPM (P = 0.09). None of the 38 patients who regularly performed HBPM were compliant with a period of rest before beginning the measurements. CONCLUSIONS: Rest before HBPM induces a bias that underestimates SBP vs. daytime ABPM and perhaps complicates patient adherence to HBPM protocols.