The aim of this study was to clarify the significance of positive rolandic sharp waves (PRS) in preterm infants with periventricular leukomalacia (PVL) and their relation to background electroencephalographic (EEG) abnormalities. We retrospectively evaluated EEG findings of 93 preterm infants; 31 infants in the PVL group and 62 in the control group. PVL was diagnosed on the basis of ultrasonographic findings. We evaluated the EEG within 3 weeks of life in this study. PRS were defined as sharp transients of positive polarity appearing in the rolandic regions with an amplitude of more than 100 microV, sharply differentiated from the background activities. The number of PRS per minute was calculated over each record. PRS were defined as present when their frequency was beyond 0.1 per minute. PRS were observed in 14 (45%) and disorganized patterns in 27 (87%) of 31 infants in the PVL group, but both were not recognized in any infants in the control group. PRS were always associated with disorganized patterns. In the first EEG, PRS were absent in 8 of 11 infants with more than two recordings, although at least one of acute or chronic stage EEG abnormalities were already present. PRS were observed in 9 of 10 infants with severe diplegia, in 5 of 11 infants with moderate diplegia and none in 10 infants with mild diplegia. The average age of the first appearance of PRS was 7.6 days. The average age of the first appearance of periventricular echodensity and cyst was 4.2 days and 21.1 days, respectively. In conclusion, PRS are related to severe deep white matter injury and could be an early marker of severe PVL. PRS appeared in combination with disorganized patterns and were considered to be incorporated into chronic-stage EEG abnormalities. Detailed evaluation of background EEG activities can be helpful in detecting PVL with a high sensitivity from the early neonatal period.