The ELZA study (Efficacite et ToLerance de ZAldiar® [Efficacy and Safety of ZAldiar®]), a large prospective observational study, recruited 5495 patients to assess the efficacy and safety of a fixed combination of paracetamol (325mg) and tramadol (37.5mg) in the treatment of moderate to severe pain. This combination was prescribed as first-line therapy in 37.6% of patients and after treatment failure in the remaining 62.4% patients, mainly after paracetamol or a step 2 analgesic such as dextropropoxyphen. The study confirmed the efficacy of this combination, irrespective of the aetiology of pain or duration of the causal disorder, on pain intensity, pain relief, quality of sleep and patient satisfaction. It was well tolerated in patients aged over 60 years (31.7% of the population), including the subgroup of patients aged 75 years or over. Only 230 (4.2%) of patients in the study reported one or more adverse events; all these adverse events were already known and were anticipated with this combination. The complementary action of its two active ingredients make this combination an effective and well-tolerated therapy for the different types of pain found in general practice.