The objective of this study was to compare the effect of different storage moisture conditions (0.90 and 0.95 water activity, a_w) and temperatures (25, 30 °C) on (1) respiration rates (CO₂; R), (2) dry matter loss (DML) of paddy and brown rice, (3) inoculation of both rice types with Fusarium verticillioides under these storage conditions on R, DML, and (4) effects on fumonisin B₁ (FB₁) contamination of these rice types. There was an increase in temporal CO₂ production with wetter and warmer conditions in naturally contaminated rice. Higher R and consequently, percentage (%) DML were generally observed for brown rice (up to 21%) while in paddy rice this was only up to 3.5% DML. The FB₁ production in paddy rice was low and similar in all treatments regardless of a_w × temperature conditions. In the dehusked brown rice there were higher levels of contamination with FB_1, with a maximum at 0.95 a_w and 25 °C. A significant correlation between %DMLs and FB₁ contamination was obtained (R=0.7454, P<0.01). These results suggest that monitoring of CO₂ may provide an early indication of fungal activity in moist rice and help in evaluating the relative risk of spoilage and potential for mycotoxin contamination.