To study the incidents of complications, adverse events and anesthetic profiles ofspinal anesthesia from primary to tertiary hospitals across Thailand. The present study is a descriptive research design. Participating anesthesia providers are requested to report the standardized incident reporting form as soon as they find the predetermined adverse or undesirable events during anesthesia until 24 hours after the operation. Data from the incident report were reviewed and analyzed to identify contributing factors and preventive strategies by consensus by three-peer reviewers. The objections were discussed and the decision was made in order to achieve general agreement. One hundred and sixty-seven cases adverse events after spinal anesthesia were reportedfrom fifty-one hospitals across Thailand. Eighty-five cases (50.9%) were male; eighty-two cases (49.1%) were female. Seventy cases (41.9%) occurred in patients whose age was more than 60 years. One hundred and thirty-one cases (78.4%) had ASA I and II, seventy cases (41.9%) occurred spontaneously whereas ninety-seven cases (58.1%) were considered as preventable. Most of the incidents (74.4%) were bradycardia (HR < 50 beats per minute). The others were hypotension (18.6%), respiratory complications (hypoxia and pulmonary edema) (5.4%), myocardial infarction (3.6%), and cardiac arrest (6.6%). Most of the incidents (88.6%) were detected by EKG pulse oximeter (64.7%), and NIBP (71.3%) respectively. Anesthetic factors and systemic factors that found to be involved in all cases were high spinal block, inadequate prehydration and delayed resuscitation. Most of the contributing factors were inappropriate decision making (45%), inexperienced performers (20%), inadequate preoperative evaluation and preparation (19%). The incidents should be minimized by having prior experience, high awareness and experienced assistants available. For immediate outcome that occurred within 24 hours, eighteen cases (10.8%) had major physiological change such as hypoxia, pulmonary edema, myocardial infarction or neurological deficit. Ten cases (6%) died within 24 hours and one case (0.6%) had cardiac arrest intra-operative period For long term outcome within 7 days, one hundred and fifty-seven reported cases (94%) had complete recovery; fourteen cases (8.4%) had prolonged hospital stay and ventilatory days. To minimize the adverse events after spinal anesthesia, the authors suggest corrective strategies which include established guideline practice, additional training, improved supervision and having quality assurance activity in each hospital.