Photocoagulation of diabetic retinopathy may provoke a number of complications. Some of them result from technical errors and can be prevented. Others may occur even if the treatment is performed by an experienced ophthalmologist. Anterior segment complications such as corneal or lenticular burns are unfrequent. Most of the complications occur in the retina. The accidental photocoagulation of the fovea is the result of a technical error. Other complications such as increased macular oedema or haemorrhages can usually be avoided by using appropriate techniques. Colour vision alterations, increased perimetric deficits or hemeralopia are often unavoidable in panretinal photocoagulation for proliferative diabetic retinopathy.