A study to evaluate the impact of primary healthy (PCH)care practices on the prevention of reinfection of soil-transmitted helminths (STH) was carried out in Nakhon Si Thammarat Province, southern Thailand. Fecal samples from the inhabitants of Ban Paruhas, the implementing village, and Ban Pungsing, the control village, were examined following mass treatment with a three-day regimen of albendazole (400 mg). Training of health volunteers, implementation of a health education program through village broadcasting system and improvements in sanitation including increasing the number of latrines were carried out at Ban Paruhas village. After one year of implementation, prevalence and intensity of STH in both villages were determined using Kato-Katz's method. Pre- and post intervention stool examination results were compared. The overall prevalence of STH at post-intervention decreased significantly in both villages, with a greater degree of reduction appearing in ascariosis and hookworm infections in the village where PHC was implemented.