This study, based on a large dataset of 894 projects from 17 infrastructure sectors, attempts to answer certain important questions on time and cost overruns in publicly-funded infrastructure projects: How common and how large are the overruns? What are the essential causes? Are contractual and institutional failures among the significant causes? What are the policy implications for planning, development and implementation of infrastructure projects? Among other results of an econometric analysis, the study shows that the contractual and institutional failures are economically and statistically significant causes behind cost and time overruns.