Twelve ruminally cannulated cows (120 ± 52 DIM; 35.5 ± 8.9 kg of milk/d; mean ± SD) were randomly assigned to treatment in a Latin square design with 21-d periods. Treatments were (1) subacute ruminal acidosis (SARA) induction, (2) recovery, and (3) control. Using indwelling pH probes, pH was measured simultaneously in the reticulum and in the rumen ventral sac (every 5 min for 24 h) on d 0, 3, 7, 14, and 21 of each period. The SARA diet contained 29% starch, 24% NDF, and 2.8% fatty acids (FA) whereas the recovery and control diets contained 20% starch, 31% NDF, and 2.3% FA. Data were analyzed as repeated measures using a mixed model. An acidosis index (AI; area under pH 5.8/DMI) was calculated for each cow to classify them as tolerant (AI < mean AI - 0.5 × SD) or susceptible (AI > mean AI + 0.5 × SD) to SARA. The average and minimum ruminal pH in cows fed the SARA diet were lower than that of cows fed the control diet on d 3, 14 and 21 (P < 0.05). As compared with control, ruminal pH remained below 5.6 for a longer time when cows received the SARA diet on d 3 (145 vs. 378 min/d; P < 0.05) and d 7 (124 vs. 264; P < 0.08). In the reticulum, the pH duration below 5.6 was greater in cows fed the SARA diet on d 3 (31 vs. 218 min/d) and 14 (8.4 vs. 127 min/d) for control and SARA, respectively (P < 0.05). The association between the ruminal and reticular pH was low (R² = 0.33; concordance correlation coefficient = 0.52, confidence interval = 0.51–0.53). Dry matter intake, milk and milk fat yield were greater in SARA-susceptible than in SARA-tolerant cows (P = 0.03, 0.06 and 0.04, respectively), whereas milk fat concentration was lower in the SARA-susceptible group (P < 0.05). Furthermore, SARA-susceptible cows had lower mean and maximal pH (P < 0.05), but minimum pH or pH variance were not different. In addition, SARA-susceptible cows had greater values for time under pH 5.8 and 5.6 (P < 0.001). In conclusion, the reticular pH measurements may underestimate the incidence of SARA and would require adjustment before this technology can be used on commercial dairy farms. The production performance of dairy cows fed high-concentrate diets was related to their susceptibility to SARA, as higher producing cows were at increased risk.