In this paper, we present a study of the polymerization of 3-hexadecyl-pyrrole (3HP) and 3-decyl-pyrrole (3DP), performed at the air-liquid interface of a Langmuir trough. In particular, we give data on. the kinetics of the process and on the compressibility of the products obtained. The comparison between the two substances has shown that 3HP is the best in terms of stability and of the quality of the layers formed. An estimation of the polymerization efficiency is given in the case of 3HP. The UV-Vis-NIR analysis made after the polymerization has shown that oligomers have been formed. This result is comparable with that obtained with a traditional "bulk" polymerization. Besides, the examination of the isotherm recorded after the polymerization shows that the polymer obtained with this method is more stable and has a better behaviour than that obtained via the traditional "bulk" method.