Earlier diagnosis and improved treatments have resulted in men with prostate cancer living for many years following diagnosis. Long-term effects of treatments are therefore important. Androgen deprivation therapy (ADT) is now commonly used to treat prostate cancer. We have estimated that, in Australia, 6500 men used ADT in 1999/2000 with a steady increase to about 21 800 men in 2009/2010 (over 300 increase), a trend similar to those in the USA and UK. ADT has a range of side-effects that can impact on quality of life such that risks and benefits should be carefully considered before making treatment decisions. Cross-sectional and longitudinal studies show that ADT can have cardio-metabolic effects including increases in fat mass and reduced lean mass, possible adverse effects on lipid levels, increased insulin resistance and increased risk of type 2 diabetes. ADT may also increase the risk of incident cardiovascular events and possibly cardiovascular mortality, although the evidence is not conclusive. In the absence of high-quality evidence to guide management, it is prudent to consider men using androgen deprivation are at higher risk of diabetes and cardiovascular disease. Maintenance of normal body weight through diet and exercise, smoking cessation, and control of blood pressure, lipid levels and blood glucose are recommended, based on guidelines for the general population. Men at significant cardiovascular risk should consider aspirin therapy. All health professionals involved in the care of men undergoing prostate cancer treatment need to be aware of the risks of ADT and ensure appropriate monitoring and management.