Information regarding the effectiveness of forest fire suppression resources that are commonly used in the boreal forest is needed for many fire management activities. In this study the relationship between the probability of containment by a medium (5 to 7 person) initial attack crew and fire size and fire intensity was investigated. Expert judgements of the probability of containment for 35 initial attack scenarios were elicited from experienced crew leaders from Alberta, Manitoba, northwestern Ontario, and the Northwest Territories. Ancillary information concerning the background and experience of each expert was also obtained. The data provided by 34 experts was statistically analyzed using repeated measures analysis and logistic probability of containment models were developed for each of the participating fire management agencies.