This study analyses trends in co-operative education (co-op) participation for graduates with a college certificate or diploma or a university bachelor's degree from 1986 to 2010 in Canada, based on data from the National Graduates Survey (NGS). Changes in co-op participation rates over time are examined, along with differences by field of study. The reasons behind the increase in co-op participation rates of women are also explored. As the number of programs and institutions offering co-op programs rose in past decades, the proportion of college graduates who participated in a co-op program rose from 7% in 1986 to 22% in 2010. Similarly, the proportion of co-op participants among graduates with a bachelor's degree rose from 5% to 12% over the same period. In 2010, the highest co-op participation rates among college graduates were found in Manitoba (32%), Ontario (31%), and Nova Scotia (27%). Among graduates with a bachelor's degree, Newfoundland and Labrador and British Columbia had the highest participation rates (19% and 18%, respectively). In 2010, 37% of graduates with a bachelor's degree in architecture or engineering participated in a co-op program--the highest co-op participation rate of all major fields of study. In contrast, the participation rate was lower among graduates with a bachelor's degree in social sciences, psychology and law (8%). Between 1986 and 2010, the co-op participation rate of graduates with a bachelor's degree in commerce, management and public administration rose from 4% to 17%. As a result, one quarter of co-op participants with a bachelor's degree were from this field of study in 2010. Of bachelor's graduates who participated in a co-op program, the proportion of females rose from 42% in 1986 to 55% in 2010, mainly because co-op participation rates have increased in fields of study that have a higher proportion of females.