OBJECTIVES: To compute the frequency of the bradycardia associated with Atenolol Hydrochloride for possible toxic signal detection (SD) by extracting the data from the Canadian Adverse Drug Reaction Monitoring Program (CADRMP) 'MedEffec'. METHODS: Appropriate statistical methods such as, Proportional Reporting Ratio (PRR); Reporting Odds Ratio (ROR); the Chi-Square (χ2) statistic; Observed to Expected Ratio (O/E) and the Du Mouchel method were used for Adverse Drug Reaction (ADR) signal detection. Significance of χ2 and other calculated statistics, e.g., PRR and ROR was based on a composite criterion of regulatory guidelines e.g. value ≥4.0 for χ2, and ≥3.0 for the rest to be considered as signal detection. RESULTS: The bradycardia associated with Atenolol Hydrochloride was 8 (A) and bradycardia associated with all other antihypertensive medicines was 48 (C). All other adverse drug reactions (except bradycardia) caused by Atenolol Hydrochloride were 235 (B) and all other ADR (but not bradycardia) associated with all other antihypertensive medicines (except Atenolol Hydrochloride) were 2593 (D).  The value of PRR was 1.8134; Reporting Odds Ratio was 1.8390 and the χ2 statistic value was 2.2915. The O/E ratio was 1.7047 and 1.6972 was the value of PRR calculated by the Du Mouchel method.   CONCLUSIONS: Atenolol hydrochloride, a selective ß1 receptor antagonist introduced in 1976 as a replacement for propranolol in the treatment of hypertension shows a number of serious and non-serious adverse drug reactions. Signal detection of bradycardia associated with Atenolol Hydrochloride was not found significant by any of the statistical method. However, since the calculated statistics were considerable, albeit not significant, the possibility of bradycardia-Atenolol Hydrochloride pairing should still be analyzed from larger databases.