We studied the incidence of positive and negative sharp waves in two pairs of twin infants with periventricular leukomalacia and compared it with that of normal cotwins by using remontage and refiltering functions of digital electroencephalography. Three electroencephalograms were serially performed in each infant. After the usual visual inspection with bipolar montage and low-cut filter of 0.5 Hz, the electroencephalogram montage was changed into monopolar derivation, and the low-cut filter into 5 Hz. The number of positive or negative sharp waves per minute, with an amplitude of more than 50 μV, was independently calculated. The number of negative sharp waves was large in the occipital and Pz areas in both infants with periventricular leukomalacia. The number of positive ones was large in the Cz area in both infants with periventricular leukomalacia. Disorganized patterns were observed in all electroencephalograms in the infants with periventricular leukomalacia on visual inspection. In conclusion, digital electroencephalography analysis using remontage and refiltering demonstrated an increased number of sharp transients in preterm infants with periventricular leukomalacia. The application of a higher low-cut filter will be useful for the assessment of sharp transients in neonatal electroencephalography.