In the past two decades European cardiologists have always been told to follow the evidence-based guidelines in their everyday clinical practice. In the case of patients with heart failure and concomitant renal disease, this universal rule is not easily applicable simply because there is a lack of specific trials in this field. Patients with cardiorenal syndromes are at risk of complications and have high morbidity and mortality. However, the management of these patients is often empirical. Drugs commonly recommended for the treatment of chronic and acutely decompensated heart failure are not always accepted for patients with concomitant renal disease. Future research trials in heart failure should include patients with renal insufficiency to allow better understanding of the impact of the current treatments available in patients with cardiorenal syndromes.