Hypokalaemia, hyperuricaemia, hypomagnesaemia and alterations to lipid and glucose metabolism undoubtedly occur with loop and thiazide diuretic treatment. Many of the metabolic effects induced by thiazide diuretics, however, can be limited by the use of low doses. Apart from precipitation of gout and worsening control of diabetes the clinical importance of these changes is slight. In hypertensive patients treated with diuretics, long-term outcome trials have shown significant benefit in terms of reduction in stroke and coronary events. Diuretics should therefore remain first-line treatment for all patients with heart failure, and in patients with hypertension except those with diabetes or gout.