Different species of fish show a variant physiological sensitivity towards environmental stressors. Metabolic rate of an organism, as an index of biochemical processes is usually indicates influenced by biotic and abiotic factors. Measuring the level of oxygen consumption and metabolite excretion is a useful tool for understanding stresses caused by the environmental factors. So at present study, the effect of two such factors, temperature and pH on metabolic rate and metabolite excretion rate of Chondrostomaregium was separately investigated. Fish specimen, Chondrostomaregium were captured by seine net (10 mm mesh size) from Dimeh Spring, which is a key tributary of the ZayandehRoud River. After acclimation of fish to the laboratory condition, pH and thermal range of tolerance were determined separately. According to the results,13 different treatments was defined, including acute (3.5-4.5°C), 24 hour (5.5-6.5°C), 1 week (5.5-6.5°C) temperature reduction; acute (30.31°C), 24 hour (29-30°C), 1 week ( 28-29°C) temperature increament; acute (4.3-4.4), 24 hour (4.3-4.4), 1 week (6.3-6.4) pH reduction; acute (9.8-9.9), 24 hour (9.8-9.9), 1 week (8.8-8.2) pH increament and control treatment (temp.=22-23°C pH= 7.8-7.9). Metabolic rate (including standard, maximum and aerobic scope) for 8 fish in each treatment was measured by intermittent flow respirometer. Metabolite excretion rate (ammonia) for each individual also was also measured by using the colorimetric method. Histopathological examination of gills and kidney of fish under different treatments were carried out by H E staining. Results showed that standard and maximum metabolic rate were increased by rising temperature in all treatments (P 0.05), however, aerobic scope didn't show significant change. Contrarily, metabolic rates reduced significantly (P 0.05) in all temperature reduction treatments as compare to the control. Significant increase (p 0.05) in standard, maximum metabolic rate and aerobic scope was observed as a results of increased pH in all treatments. Standard metabolic rate showed significant increase (P 0.05) in all methods of pH reduction treatments, but maximum metabolic rate and aerobic scope increased significantly only in 24 hour and 1 week reduction treatments (P 0.05) as compere to the control. Ammonia excretion showed significant increase (p 0.05) in all groups treated with an increased temperature and pH except for temperature reduction at 24 hours which showed significant reduction (P 0.05) as compere to the control group. Ammonia excretion only showed a significant increase (P 0.05) when the acute reduction in pH was experienced by fish, but not in 24 hour and 1 week treatments groups. Histopathological damages such as hyperplasia, clubbing, change in secondary lamella length were generally observed in the gills of most treated fish. Kidneys of treated fish specimen's also showed the damages such as dilation of tubules, atrophy, glomerular shrinkage, necrosis, loss of tubules and hypertrophy. Based on the results of the present study it could be stated that environmental temperature increment as well as pH reduction and increment acted as a loading stressor to Chondrostomaregium . But environmental reduction in temperature acted as a limiting stressor. Key word : Oxygen consumption rate, aerobic scope, ammonia, gill and kidney histopathology