An ATR-FTIR spectrometry technique with light conduit and diamond-composite sensor was used to perform in-line monitoring of butyl acrylate, methyl methacrylate, and vinyl acetate batch emulsion homo- and copolymerizations. This technique was found to be ideal for determining individual monomer conversions and copolymer composition changes as a function of time when those polymerizations were carried out in aqueous media. The results obtained from the ReactIR(TM) 1000 reaction analysis system agreed well with those determined by traditional gravimetric and H-1-NMR spectrometry methods.