We use a Markov model to calculate the expected medical, disability, employee replacement, life insurance, and pension costs to a business firm for an HIV-infected employee. This analysis differs from previous HIV/AIDS cost analyses because we take the perspective of a business firm rather than of society, and we focus on the expected costs over a time frame relevant for business decision making. The maximum expected five-year cost to a business firm for an HIV-infected employee is estimated at $32,000, with an average expected cost of $17,000. These expected employment-based costs are less than the lifetime medical AIDS costs to society for an individual, which are estimated at more than $85,000. Employment-based costs are most influenced by the type of benefits provided under employer-based health insurance plans.