The paper discusses preliminary performance and cost estimates of mercury emission control options for electric utility boilers. Under the Clean Air Act Amendments of 1990, EPA had to determine whether mercury emissions from coal-fired power plants should be regulated. To aid in this determination, preliminary estimates of performance and cost of activated-carbon-based mercury control technologies were developed, based on relatively few data points from pilot-scale tests. The paper presents the methodology used in arriving at these estimates, estimated capital and annual operation and maintenance costs, and results of sensitivity analyses conducted on these cost estimates. Results reveal that, for most applications, capital costs of activated carbon injection (ACI) mercury control technologies may be comparable to those associated with low nitrogen oxide burners (LNBs).