The welfare of children has come under close scrutiny by state and federal agencies as a result of alleged exposures in and around dwellings following the use of a host of chemicals either in the air or on contacted surfaces. A study protocol was designed to specifically measure the exposure of adults and crawling children to insect control agents on grass and carpets. The design was established to measure exposures through three routes: inhalation, dermal, and the ingestion of chemicals from the hands, which is unique to children. Chlorpyrifos, an organophosphate insecticide sold under the trademark of Dursban, was the test substance used in a series of studies. Air sampling was conducted to determine time-weighted average exposures for specific periods of time. By using reference breathing rates, inhalation doses were estimated. To determine dermal exposure and eventually dose, dislodgable residues were determined by dragging a weighted block and coupon across 4-lineal ft (1.22 m) of treated surface. The weighted block, 8.5 lb (3.86 kg) of lead over a 9 in.2 (58.1 cm2) piece of plywood, provided a pressure similar to the pressure exerted by a crawling or walking one-year-old child. Dislodgeable residues were determined in micrograms (μg) of removed chemical per square foot (929 cm2) of surface. By estimating contact surface, dermal exposure in micrograms of substance was determined. Dermal dose was the product of exposure (μg) and percent absorbed through intact skin, a value obtained from earlier work with human volunteers. Hand rinses using a dilute anionic surfactant mixture followed by a distilled water rinse were used to determine hand/oral exposures and the ingestion dose unique to children. In addition, human pharmacokinetic data was available for chlorpyrifos. This allowed for biomonitoring of the urine of the human adult volunteers who conducted various activities on the treated surfaces. Using the physicochemical monitoring data and biomonitoring data, the adult chlorpyrifos dose was estimated both ways. Agreement between the physicochemical method and the biomonitoring method for the adult dose was excellent. The child's dose was estimated by using physicochemical measurements and adult urinary biomonitoring data in conjunction with one another.