OBJECTIVES: To assess the clinical effectiveness of Betaloc ZOC (metoprolol succinate), metoprolol tartrate or carvedilol in a treatment of primary arterial hypertension. METHODS: Systematic review of published clinical trials selected in accordance with Cochrane Collaboration guidelines was conducted to assess effectiveness and safety of the drugs in hypertension treatment. Systematic review was conducted in August 2005; Medline (Pubmed) Cochrane and EMBASE were searched to find relevant clinical trials. Only randomized clinical trials with credibility assessment of two or more points according to Jadad scale were included in the systematic review. In case no clinical trials with “head to head comparison” between metoprolol succinate and metoprolol tartrate or carvedilol were found, indirect effectiveness assessment with a common reference was done. Clinical data was pooled with RevMan 4.2. RESULTS: Six relevant clinical trials with direct comparison of metoprolol succinate and metoprolol tartrate were found. Pooled clinical data on probability of diastolic pressure normalization (BP < 95 mmHg) in case of Betaloc ZOC use compared to metoprolol tartrate revealed insignificant trend favouring Betaloc ZOC (respectively 69.2% vs. 63.4%); no significant difference in safety profile was shown between the drugs (respectively 40.7% vs. 41.9%). Systematic review revealed no randomized, “head to head comparison” clinical trials with metoprolol succinate and carvedilol; indirect comparison of the drugs with atenolol as a common reference was done to assess their clinical effectiveness. Indirect comparison showed superiority of Betaloc ZOC over carvedilol in hypertension treatment (respectively: 81% vs 71.4%); no significant differences in safety profile were revealed. CONCLUSION: Betaloc ZOC use in place of metoprolol tartrate or carvedilol lead to higher clinical effectiveness in primary arterial hypertension treatment.