Heart failure has a high prevalence and it has a poor prognosis despite the advances in pharmacological treatment. Cardiac resynchronization therapy with biventricular pacemaker has a clinically proven efficacy in the treatment of heart failure with intraventricular dyssynchrony. Conventionally the therapy is indicated in severe drug refractory heart failure (NYHA III-IV) with optimal drug treatment, increased QRS duration (> or = 120 ms), echocardiographic parameters (left ventricular ejection fraction at most 35%). Implementation of new methods (tissue doppler echocardiography, CT, MRI, electroanatomical mapping) can help to select potentially responding patients. Individual optimization of therapy can be performed with non-invasive and invasive methods, the efficacy can be improved even in responding patients. Due to the outstanding efficiency widening the indications is a must. Currently, the efficacy is being investigated in mild heart failure and patients with narrow QRS. Several other questions (transvenous or surgical implantation, need of an implantable defibrillator) will be answered in future trials.