Abstract: Powdered tablets (100-150 mg) were dissolved in 7 mL CHCl3. The solution was filtered and the filtrate was made up to 10 mL. For flow injection (FI) measurements, a portion (300 µL) was injected into a carrier stream of CHCl3 at a flow rate of 1.23 ml/min. A FTIR spectrum was recorded, accumulating 2 scans. Stopped-flow measurements were also made on the CHCl3 solution of the sample, 16 scans being accumulated. In both cases, a 0.5 mm bandpass and a nominal resolution of 4 cm-1 were employed. Propyphenazone (I) was determined by measuring the peak-height absorbance at 1595 cm-1, corrected with a baseline established from 2000-890 cm-1. Caffeine (II) was determined by measuring the first-derivative peak height at 1712 cm-1. Detection limits were 0.03 mg/ml I and 1.5 mg/ml II for the FI mode; RSD were 1-2.1% (n = 5). Detection limits were 0.06 mg/ml I and 0.45 mg/ml II for the stopped-flow mode; RSD was 0.5% (n = 5). A distillation unit was incorporated into the FI manifold for online recycling of the CHCl3 used as carrier and solvent, thus avoiding the generation and accumulation of toxic waste. A procedure is proposed for the simultaneous FTIR determination of propyphenazone (PFZ) and caffeine (CAF) in pharmaceuticals. The method involves the dissolution of the active principles in CHCl3, followed by filtration of sample solutions to remove the excipients. PFZ is then determined by absorbance measurements at 1595 cm-1, using a baseline established between 2000 and 890 cm-1, and CAF by using the first-derivative values at 1712 cm-1, using solutions of PFZ and CAF for external calibration. The method was applied in both the stopped-flow and flow injection modes, providing precise and accurate results for the analysis of real samples. The incorporation of a distillation unit for the on-line recycling of the CHCl3 used as carrier and solvent provides an environmentally friendly analytical methodology which makes possible an injection frequency of 120 samples h-1 and reduces the cost and side-effects of the production of laboratory waste.