Background: group B streptococcus (GBS) can cause significant morbidity in pregnant women. Manifestations of symptomatic maternal infection include chorioamnionitis, endometritis, cystitis, pyelonephritis and febrile GBS bacteremia. Objective: this work aimed to assess the effectiveness of penicillins versus erythromycin in treatment GBS infection following PPROM. Patients and Methods: the study included 50 pregnant females presented with PPROM before 36 weeks gestation who were attending to Outpatient Obstetrician Clinic at El Sayed-Galal University Hospital. The cases were classified into 2 groups, 25 cases each as follows: Group A (penicillin- treated group) and group B (erythromycin-treated group). Results: the results of the study showed that there were no significant difference between the cases within the two study groups as regard the different demographic data, the obstetric history and the state of the current pregnancy. There was a significant difference between the two groups as regards the fetal and maternal outcomes being less in group A (penicillin-treated group). Conclusion: our study revealed the superiority of penicillin over erythromycin in treatment of GBS associated maternal infections.