Specific reactions of amino and carboxyl end groups of Nylon 6 with the reactive oxazoline groups belonging to a cyclophosphazene compound (referred as CP20XA) were carried out at 240 degrees C for different times, under inert atmosphere. Ny6 polymers terminated with one specific reactive chain end (-COOH or NH2) were reacted with different amounts of CP2OXA to study the kinetic order of the reactions. All Ny6-CP2OXA reacted products soluble in trifluoroethanol (TFE) were well characterized by MALDI-TOF MS, FT-IR and (H-1-1 and C-13) NMR techniques. The MALDI-TOF results show that the oxazoline rings react with the carboxyl chain ends of Ny6 following second-order kinetics. The reactions with amino chain ends are very fast and high amounts of gels are produced in just 5 min heating, whereas traces of gel are formed when Ny6COOH and CP-20XA are reacted for 60 min. The gels were characterized by FTI R analyses. and also by MALDI-TOF MS after partial acid hydrolysis. NIALDI-TOF mass spectra reveal also that oxazoline rings can react with -NH amide group,", along the Ny6 chains, and with secondary amino groups formed by a condensation reaction involving the elimination of ammonia from two amino chain ends, These side reactions could be responsible of the formation of the gels. The polymerization ofCP20XA was also observed, and the oligorners formed could also react with Ny6 samples during the melt mixing.