The relationship between the profilograph profile index (PI) and the international roughness index (IRI) is evaluated. To accomplish this evaluation, profile data taken on 48 overlaid test sections were used in profilograph simulations to predict the profilograph response to the measured profiles. The PIs determined were then correlated with IRIs computed from the profile data to evaluate relationships between these roughness statistics. The results show that the PI based on the null blanking band is more strongly related to the IRI than the corresponding index determined using the 5-mm blanking band. In view of the general acceptance of the IRI as a statistic for establishing surface smoothness based on profiles, the results suggest that a profilograph specification based on the null blanking band is preferable to a similar specification based on the 5-mm blanking band, which may mask certain components of roughness that are otherwise picked up if no blanking band is used.