Member states of the International and Collaborative Effort (ICE) are the United States of America, England and Wales, Denmark, Bavaria and North Rhine-Westphalia of the Federal Republic of Germany, Israel, Japan, Norway, Scotland and Sweden. The group has collected, analysed and compared distributions of birthweight for member countries, where available from 1970 onwards, for singleton and all livebirths, stillbirths, early and late neonatal and postneonatal deaths. The present paper is an account of the differences in birthweight distributions, and trends over time seen between and within countries, for livebirths and stillbirths. The major findings are the relative robustness over time of the parameters which characterize the distribution of birthweight within countries, and the marked and consistent differences between these distributions in different countries.