Quality patient care must be the underlying principle of any nation's health system and it is important that health care organizations develop a systematic approach to monitoring and evaluating the quality of healthcare provided. Very few empirical studies have been made in Thailand of Total Quality Management (TQM) activities in accredited hospitals and their relationships to both the length of time elapsed since accreditation and obstacles. This study investigates the TQM activity level, obstacles and barriers. An 80-item TQM assessment scale developed from the Malcolm Baldrige framework was used to measure the level of TQM activity in accredited hospitals. Fifty two Quality Managers at accredited hospitals in Thailand were asked to respond to the mailed questionnaire survey, which resulted in a response rate of 79%. The results revealed that the TQM activity level is within the range of "neutral to agree" (3.82) on a 5-point scale. 'Senior Executive Leadership' achieved the highest score (4.09) followed by 'Quality Management' (3.97) and 'Information and Analysis' (3.90). There was no significant difference of TQM activity levels between any of the hospitals. The relationship between TQM activity and the length of time at an accredited hospital was statistically significant. The significant TQM activity dimensions relating to length of time at accredited hospital as shown by partial correlation coefficients were human resource management (-0.3966, p < 0.05), quality and operational result (-0.3911, p < 0.05), quality management (-0.332, p < 0.05), senior executive leadership (-0.3276, p < 0.05), strategic quality planning (-0.3197) and customer satisfaction (-0.3197, p < 0.05). With longer time at an accredited hospital the TQM activities decreased. It appears that the most important contributing factors to TQM activities in accredited hospitals were continuous internal and external surveys, employee participation and involvement, and commitment of the lead team. The most difficult barrier to TQM activities in accredited hospitals is staff fatigue and turnover rate. These study findings can serve as the basic knowledge necessary to improve quality management in accredited hospitals.