OBJECTIVE: To assess the cost-effectiveness of a law banning the use of cellular phones by drivers in the Canadian province of Alberta. METHOD: Cost-effectiveness analysis using a probabilistic decision-analytic model and publicly available data. We adopted a societal perspective. Health gains were measured in terms of quality-adjusted life-years. Costs include those associated with awareness raising, enforcement and the welfare loss associated with the reduction in cellular phone use, less savings in health care and other costs associated with automobile accidents. RESULTS: A ban promotes health and releases resources worth more than the costs. There is an 80% chance that a ban will be 'cost saving', and a 94% chance that a ban will cost less than Can$50,000/QALY. The results are sensitive to the additional risk posed by cellular phone use while driving, and the rate and pattern with which drivers comply with a ban. CONCLUSION: Under our base line assumptions a cellular phone ban is likely to be cost saving from a societal perspective. The results are sensitive to parameters for which there is very little information or for which the available information is contradictory.