Currently, there are between six and eight million workers employed in the U. S. construction industry.(1) When compared to all other goods-producing industries, construction leads in the number of occupational injuries and illnesses.(2) This industry consists primarily of small contractors, each employing fewer than 10 workers. Small contractors employ 30 percent of all construction workers, and represent 82 percent of the total number of construction establishments.(3) Small contractors are not subject to the Occupational Safety and Health Administrationís (OSHA) injury and illness reporting requirements, which are mandatory for employers with more than 10 employees. Considering that small establishments represent such a large segment of construction employers, it is likely that the injury and illness statistics for the industry are underestimated. Recent articles have identi. ed potential chemical and physical hazard exposures in construction environments.(4,5,6) Specifically identi. ed are exposures to hazardous solvents, wood dusts, noise, vibration, and temperature extremes, which are more common in construction than in other more traditional work environments.(5,6) Beginning in January and continuing in May through July 1999, the National Institute for Occupational Safety and Health (NIOSH) investigators and their contractors conducted pilot studies in Columbus, Ohio and Denver, Colorado. The studies were conducted during different phases of residential construction performed by six general contracting companies and their subcontracted tradesmen. Investigators visited 20 residential construction sites (i.e., lots), consisting of different house floor plans. This surveillance research effort was initiated to develop a methodology for the identi. cation and quanti. - cation of chemical and physical hazards in residential construction, an industry with a high percentage of small contractors. This report is intended to inform the reader of the chemical and physical hazard evaluation methodology developed by NIOSH for use on residential construction sites, and how it has been successfully applied within the recently completed pilot studies.