There are many possible approaches to ‘routine’ castration of horses with normally descended testicles and the approach utilised is generally decided by the clinician. Unfortunately, complications are relatively common after castration, ranging from rates of 10–60% of animals, therefore knowledge of their predispositions, signs and management is essential to prevent further morbidity and mortality. Reported complications include excessive swelling, haemorrhage, infection (including clostridial infections), funiculitis, peritonitis, eventration, penile trauma +/- paralysis, hydrocoele formation, continued stallion-like behaviour and anaesthetic complications. Most complications are not considered life threatening and do not require emergency treatment; the exceptions are eventration, haemorrhage, peritonitis and clostridial infections, all of which are potentially life-threatening.