The design of packed towers for the removal of volatile organic chemicals (VOCs) depends strongly on compound volatility and rates of mass transfer. Uncertainty in Henry's constant and mass transfer coefficients greatly affects the predicted performance of completed packed-tower treatment systems. This research focuses on evaluating the reliability of packed-tower aeration designs by modeling Henry's constant and mass transfer coefficients as random variables with established distributions using Monte Carlo simulation. A case study consisting of alternative designs to achieve a given required contaminant removal is presented to show how design parameter uncertainty affects the predicted system performance and the cost of resulting designs. It was demonstrated that the probability of failure is an important design consideration in addition to cost and that full consideration of design alternatives will include design parameters outside of those that offer a given deterministically predicted performance. Includes 54 references, tables, figures.