To study the incidence and clinical manifestations of rotavirus among children at Buri Ram Hospital, admitted with the diagnosis of acute diarrhea between November 2005 and February 2006. In the course of a cross sectional descriptive study, 103 stool samples obtained from inpatients below the age of 5 years were examined for rotavirus by RT- PCR. Data on clinical manifestations, complications, administration of antibiotics, length of admission and hospital cost were obtained by means of questionnaires distributed among physicians. The statistics used were presented as percentage, mean and 95% confidence interval, while chi-square and unpaired t-test were used to establish significant differences at p < 0.05. Rotavirus was detected in 45 of 103 stool samples (43.68%, 95%CI = 33.93, 53.81). No significant differences were found between clinical manifestations of children with rotavirus infection and non-rotavirus infection as both groups displayed acute watery diarrhea (p = 0.33), fever (p = 0.80), nausea or vomiting (p = 0.08), predominant lymphocytes (p = 0.54), absence of red blood cells (p = 0.63) or white blood cells (p = 0.57) in the stool examination, moderate or severe dehydration (p = 0.06), lactose intolerance (p = 0.41), hypokalemia (p = 0.55), metabolic acidosis (0.18) Administration of antibiotics was significantly reduced for treatment of rotavirus acute diarrhea (31.1% vs 63.8%, p = 0.001). Hospital cost and length of admission were significantly reduced in rotavirus acute diarrhea (1,845.04 baht vs 2,297.00 baht, p < 0.01) (2.09 days vs 2.81 days, p < 0.001). Compared to previous studies, no differences were found in the percentage of rotavirus acute diarrhea. Rotavirus infection is a major cause for hospitalization of children below the age of 5 years with acute diarrhea. Clinical characteristics of rotavirus acute diarrhea were not significantly different from those due to other etiologies. Diagnosis of rotavirus infection should be based on various clinical manifestations and specific laboratory methods. Further studies on the cost benefit of rotavirus vaccine in Thailand ought to be performed before implementing a universal vaccination program.