Background : Urinary tract stone disease is endemic in North and Northeast Thailand. Kalasin, one of the poorer provinces of the Northeast, has one of the highest incidences of the disease. The frequency of the types of stones is unknown but such information is necessary for prevention programming. Objectives : To study the incidence of urinary stone disease and stone composition in Kalasin Province. Design : Prospective and descriptive study. Setting : Kalasin Hospital, Kalasin Province, and Rathviti Hospital, Bangkok. Subjects : Patients (n = 230) with urinary tract stones admitted to kalasin Hospital between August and December, 2000. Method : Collected signs and symptoms at presentation, routine lab results, IVP surgical procedures used for treatment and results of infrared stone analysis. Results : Men outnumbered woman 1.8 to 1. The age range among the men was 41 to 50 years. Most were farmers who had completed elementary school. Patients came mostly from either Yangtalad or Kuchinarai District and side pain was the most common presentation. Renal calculi, the most stones, comprised calcium oxalate, calcium phosphate and magnesium ammonium phosphate. Nephrolithotomy was most common treatment. Conclusion : Urinary tract stone disease occurred primarily in patients of low socioeconomic standing (64%). Calcium oxalate was the most common mineral composition of the stones whether they were found in the lower or upper tract. All cases were treated Surgically. . . .