This paper explores the feasibility of using in-line Raman spectrometry to monitor different monomer-solvent-polymer systems by different techniques: in-line, by an immersion probe; in-line, but externally aiming the spectrometer through the glass of the reactor wall; and off-line, taking the samples in small vials. The monitoring of chemical systems was done in the absence of polymer in order to simplify and facilitate the initial studies as well as in polymerization reactors operated with different processes: coordination polymerization of styrene-myrcene, anionic polymerization of myrcene, styrene emulsion polymerization, and methyl methacrylate-butyl acrylate mini-emulsion copolymerization. In all of these systems, it is of interest having an online monitoring technique for feedback control which would increase the productivity of the process, the quality of the product and the safety of the operation. Results show that Raman spectrometry was always capable to reproduce the trend of the process, with reasonable deviation with respect to gravimetric analysis.