The paper discusses the Hazardous Air Pollutant Program (HAP-PRO), version 1.0, automated hazardous air pollutant (HAP) and volatile organic compound (VOC) control technology assessment software, designed to assist permit engineers in reviewing applications for control of air toxics. The program is used to calculate the capital and annual costs of implementing six different VOC and three different particulate control devices, including selected engineering parameters, which may be used to help review the engineering design values. HAP-PRO functions as an 'expert system.' Users with limited knowledge of design calculations and costing methodologies can determine the approximate costs of implementing a control device. The tedious and complex calculations are performed for the user. A secondary purpose of HAP-PRO is to generate lists of all facilities containing (1) a specific pollutant in their emission stream(s), or (2) a specific type of emission stream (organic or inorganic vapor and particulate). With such reports, the user can quickly determine which sources are emitting a given pollutant if further investigation is warranted. HAP-PRO also performs the role of a traditional data base management system (DBMS) by allowing queries to be performed of its data base.