To determine whether a centralised telephone intervention reduces the incidence of death or admission for worsening heart failure in outpatients with chronic heart failure. Multicentre randomised controlled trial. 51 centres in Argentina (public and private hospitals and ambulatory settings). 1518 outpatients with stable chronic heart failure and optimal drug treatment randomised, stratified by attending cardiologist, to telephone intervention or usual care. Education, counselling, and monitoring by nurses through frequent telephone follow-up in addition to usual care, delivered from a single centre. All cause mortality or admission to hospital for worsening heart failure. Complete follow-up was available in 99.5% of patients. The 758 patients in the usual care group were more likely to be admitted for worsening heart failure or to die (235 events, 31%) than the 760 patients who received the telephone intervention (200 events, 26.3%) (relative risk reduction = 20%, 95% confidence interval 3 to 34, P = 0.026). This benefit was mostly due to a significant reduction in admissions for heart failure (relative risk reduction = 29%, P = 0.005). Mortality was similar in both groups. At the end of the study the intervention group had a better quality of life than the usual care group (mean total score on Minnesota living with heart failure questionnaire 30.6 v 35, P = 0.001). This simple, centralised heart failure programme was effective in reducing the primary end point through a significant reduction in admissions to hospital for heart failure.