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In the current study, the chemistry of fresh and stored rainwater of Thar Desert, Pakistan, was estimated during two consecutive monsoon periods. The present research deals with the variation in physicochemical parameters, total arsenic (As-t), inorganic arsenic species (As-i, As-V, As-III), and fluoride (F-) in stored rainwater (SRW) at different time intervals (1 week to 3 months). The pH of fresh rainwater (FRW) samples showed slightly acidic to neutral in nature (6.08-7.06) which were inconsistent with the reference pH value (5.6) of rainwater. The resulted data indicated that As-t and F- levels in SRW were enhanced with time duration. The levels of As-t and F- in SRW after different time intervals were found in the range of 194-683 mu g/L and 10-35.4 mg/L, respectively. The values of As-t and F- were 20-70 and 7-24 times higher than those of WHO permissible limits, 10 mu g/L and 1.5 mg/L, respectively. The As-III was dominant species in SRW, which corresponds to > 60 % of As-i. The characteristics of the SRW revealed an unacceptable quality to consume for drinking and agricultural purposes in the studied area.