Although ICUs generate attention as consumers of resources, no national data on utilization and costs were available in Canada. U.S. estimates are too old for current comparison. Based on national hospital survey data from Statistics Canada, we calculated the utilization of ICUs in all Canadian general hospitals from 1969 to 1986 and estimated costs for 1986. Using the American Hospital Association's Annual Survey, we estimated comparable trend data from U.S. hospitals for the period of 1979 to 1986, and national ICU costs for 1986. The results demonstrated steady growth in Canadian utilization from 1969 to 1986, with increased ICU patient days (17 to 42 days/1000 population). National costs for 1986 were estimated at $1.03 billion (Canadian), which was roughly 8% of total inpatient costs and 0.2% of Canada's gross national product (GNP). Utilization trend data for the United States showed a rapid increase from 1979 through 1982 with slower growth after that. In the United States, ICU utilization in 1986 was estimated at 108 patient days/1000 population. Total ICU costs were estimated at $33.9 billion (U.S.), which is 20% of all inpatient hospital costs and accounts for 0.8% of the GNP. ICU utilization in the United States is 2.5 times that of Canada.