Several caries activity tests were used to investigate the caries risk of patients with Fixed orthodontic appliances. Twenty young individuals, with a mean age of 11 years, participated in this study. Ten subjects were free of any orthodontic appliances and formed the control group. The other 10 individuals had been wearing fixed orthodontic appliances for at least 4 months. Stimulated saliva samples were obtained from all patients. Saliva samples were used to investigate the salivary flow rate, the salivary buffer capacity, and mutans streptococci and lactobac illi counts. The orthodontic patients exhibited a significant increase in salivary flow rate. Results of statistical analyses were nonsignficant in all other tests, suggesting that fixed orthodontic appliances are not the sole factor increasing the patient's caries risk during orthodontic treatment.