Fifty-one patients after myocardial infarction (age 63 ± 6.3 [between 41 and 77] years; ejection fraction 43 ± 12.3 %) and 40 healthy subjects were monitored. Their 7-day/24-hour records, part of the Brno database, were analyzed chronobiologically. The left ventricular mass index (LVMI), considered as gauge of cardiovascular risk, is greatly elevated when abnormal circadian patterns of diastolic (DBP) and systolic blood pressure (SBP) are diagnosed in hypertensive patients. This study aimed at determining any relationships between LVMI and circadian and circaseptan amplitudes of systolic (S) and diastolic (D) blood pressure (BP) in patients after myocardial infarction. The patients were subjected to controlled ambulatory rehabilitation program lasting for 12 weeks, three times a week. During rehabilitation and blood pressure recording, they did not change pharmacotherapy (ACE inhibitors, statins, beta-blockers or calcium antagonists). The patients underwent 7-day ambulatory blood pressure monitoring (TM-2421 from A&D, Tokyo, Japan). The data were analyzed, using Halberg’s cosinor method. A 24-hour cosine curve was fitted by least squares and its parameters were evaluated every day: the rhythm-adjusted mean value (MESOR), the circadian amplitude (half the predicted extent of change within a day) and the circadian acrophase (a measure of the timing of overall high values recurring each day). The circaseptan amplitude was estimated by fitting a 7-day (168-hour) cosine curve to the data. LVMI was determined by echocardiography. SBP and DBP mean (± SD) values were 122.4 ± 7.9 and 74.7 ± 8.1 mmHg respectively. The average circadian amplitude of SBP was 7.2 ± 4.8 mmHg and that of DBP was 5.6 ± 2.8 mmHg. The average circaseptan amplitude of SBP was 3.9 ± 2.0 mmHg and that of DBP was 3.0 ± 1.6 mmHg. The average LVMI was 121 ± 33 g/m2. LVMI did not correlate with the mean, circadian or circaseptan amplitude of SBP or DBP. In contrast to results for hypertensive patients, a relationship between LVMI and the circadian and circaseptan patterns of SBP and DBP was not found in patients treated after myocardial infarction.