As part of an oral health survey concerned with the evaluation of a collaborative primary oral health care program, the CPITN system was used to determine the periodontal status and treatment needs of 2009 Thai people aged 12-44 yr. Calculus dominated the CPITN scores. The percentage of persons with healthy periodontal tissues was small, ranging from 0.7% at age 35-44 to 4.1% at age 12. Ranges for other highest scores were bleeding-0.4% at age 35-44 yr to 6.1% at age 12 yr; calculus-62% at age 35-44 yr to 92.6% at age 17-18 yr. Pocketing did not occur to any significant extent until age 35-44 where 23.9% had 3-5 mm pockets and 12.8% had pockets 6 mm or deeper. 15-18-yr-olds who had received prior care from a Village Scaler had a significantly higher number and proportion of healthy sextants than those who had not received such care. No such effect was demonstrated in 35-44-yr-olds. The need for caution in the interpretation of this result is stressed. Attention is drawn to the desirability of differentiating between supra- and sub-gingival calculus in the CPITN scoring system and to the excessive treatment requirements that arise from classifying everyone with calculus as requiring prophylaxis and scaling. A great deal of improvement will need to be affected if the Thai national and global goals for periodontal health are to be achieved in the districts covered by this survey.