The purpose of this study was to determine the alterations in the chromium and nickel concentrations in the saliva of orthodontic patients treated with fixed orthodontic appliances. Forty-five orthodontic patients were included in this study. The first group consisted of 15 patients (7 female, 8 male) with fixed appliances placed in their upper and lower arches. The second group consisted of 15 patients (8 female, 7 male) with a fixed appliance placed only in the upper arch. The control group consisted of 15 patients (7 female, 8 male) who were not undergoing orthodontic treatment. Four samples of stimulated saliva were collected from each patient before insertion of the fixed appliance, 1 week after insertion of the appliance, 1 month after insertion of the appliance, and 2 months after insertion of the appliance. The same 4 samples of saliva were collected from each control patient at the same time intervals as for the fixed-appliance groups. The chemical analyses were done with an electrothermal atomic absorption spectrophotometer (Perkin Elmer 2380, Perkin Elmer Corp, Baden Seewerk, Germany). The Wilcoxon matched-pairs signed ranks test was used to test differences between samples before and after insertion of orthodontic appliances. A Kruskal Wallis 1-way analysis of variance was used to test differences in nickel and chromium concentration among the 3 test groups. It was observed that there was a large variation in the concentrations of both nickel and chromium in saliva. No significant differences were found between the no-appliance group and the samples obtained after insertion of the appliances. The results of the study suggest that fixed orthodontic appliances do not significantly affect nickel and chromium concentrations of saliva during the first 2 months of treatment. (Angle Orthod 2000;70:000-000.).