The aim of this study was to compare blood pressure rise after interruption of two angiotensin converting enzyme (ACE) inhibitors in hypertensive patients. After a 2-week placebo run-in period, hypertensive patients were treated with either trandolapril 2 mg once daily or perindopril 4 mg once daily for 4 weeks in a double-blind design. A placebo was then administered for 1 week. Three periods of 1-week home self-measured blood pressure (SMBP) were programmed: end of placebo run-in period, end of treatment period, and final withdrawal placebo period. Every day, three consecutive measurements were requested both in the evening and in the morning. Individual reversion to baseline BP level was studied in the subgroup of patients responding to therapy (evening diastolic SMBP decrease > or =6 mm Hg). The ratio (R) of mean post-drug DBP lowering (residual effect) over evening on-drug DBP lowering (full effect) was used to study reversion to baseline. Patients exhibiting a lower value than the median of this ratio were called Reverters, whereas others were called Nonreverters. One hundred-nineteen patients entered the analysis. During the treatment period, mean SMBP decreased significantly, from 150 +/- 14/97 +/- 7 mm Hg to 139 +/- 15/91 +/- 9 mm Hg (all P < .001). The on-drug BP level was similar in the evening in the two treatment groups. However, both systolic and diastolic morning SMBP levels were significantly lower in the trandolapril group. After drug discontinuation, the mean BP level significantly rose to 144 +/- 14/94 +/- 9 mm Hg (all P = .01) but remained lower than the baseline BP values (P = .003 for SBP and P = .002 for DBP). The post-drug BP level was significantly lower in the trandolapril group than in the perindopril group. Seventy-four patients were responders to therapy. In this subgroup, the median of the R ratio used to analyze reversion to baseline after drug discontinuation was 44%. Nonreverters were characterized by a sustained on-drug BP decrease, compared to Reverters. We therefore conclude that ACE inhibitor treatment withdrawal is accompanied by a rapid rise in BP (within 48 h), followed by a 5-day BP plateau that is lower than the initial level. Reverters to baseline after drug discontinuation were more likely to be insufficiently controlled during therapy, particularly in the morning. The longer duration of action of trandolapril was associated with a lower BP level during both the morning during the active treatment phase and the 1-week posttreatment phase.