Pathological features on very premature EEG concern background abnormalities and abnormal patterns. Positive rolandic sharp waves keep an important place regarding diagnosis and prognosis. Background abnormalities give essential complementary informations. Unusual patterns (abnormal localisation or morphological aspect, high amplitude) remain early markers of cerebral lesions. Analysis of these pathological features must always take into account treatment given to the baby, which can by itself modify the EEG.