Abstract Abnormalities in neonatal sensory evoked potentials (EPs) may indicate a poor developmental prognosis, but such EPs are highly variable, changing with development, and requiring subjective analysis. ‘Weight of Evidence’ ( W), the logarithm of the ratio of the probability that a response has occurred to the probability that it has not, and ‘Response Entropy’ ( S), the spread of the response over time and frequency bands, might provide objective and quantitative measures of EP abnormalities and developmental changes, based on information processing characteristics. W and S were calculated from visual and somatosensory EPs recorded in 72 premature newborns over 2 sessions, separated by 6–9 weeks. Group 1 had normal brain ultrasound images at the time of recording, and a normal developmental outcome at age 2 years. Group 2 had abnormal brain ultrasound images but normal outcome. Group 3 had abnormal brain imaging and abnormal outcome . W values were lowest in Group 3 (visual p < 0.001: somatosensory p < 0.04). Entropy diminished between sessions (visual p < 0.001: somatosensory p < 0.015): it was highest in Group 2 (visual p < 0.03). The low W in Group 3 implies a lower signal/noise ratio, reducing information capacity. Decreasing entropy suggests more efficient information encoding with maturation.