Objective: To evaluate and compare the efficacy of gentamicin, amoxicillin and metronidazole (GAM) antibiotic paste in noninstrumentation and instrumentation techniques in infected primary molars. Methods: Sixty primary molars in children of 4 to 8 years were selected and divided into four groups: teeth without any periapical or furcation involvement undergoing pulpectomy by noninstrumentation (Group N1) and instrumentation (Group N2) technique using GAM antibiotic paste; teeth with periapical or furcation involvement undergoing pulpectomy by noninstrumentation (Group R1) and instrumentation (Group R2) technique using GAM antibiotic paste. Regular follow-up at 3, 6 and 12 months was carried out for each group and all the clinical and radiographic changes were evaluated statistically using SPSS software. The level of significance was set to P 0.05. Results: Overall, 73.3% of success was observed in Group N1, 71.4% in Group N2, 86.7% in both Group R1 and Group R2 (P = 0.003). Conclusion: The GAM lesion sterilisation and tissue repair (GAM-LSTR) technique can be an alternative to conventional pulpectomy. Keywords: antibiotic paste, primary molars, pulpectomy, gentamicin, amoxicillin, metronidazole