Purpose: This study utilized multiple genetic analyses to detect evidence of maternal MS acquisition in children with S-ECC. Methods: Twenty-seven mother/child pairs were selected from children with S-ECC preceding dental rehabilitation under general anesthesia. Plaque samples were collected from the mother, child, and the child's carious lesion. Arbitrarily primed-polymerase chain reaction (AP-PCR) genotyped 6-8 MS isolates from each plaque sample, and unique genotypes were identified. Representative MS isolates with unique genotypes were characterized by pulsed-field gel electrophoresis (PFGE). Cluster analysis using the Dice band-based similarity coefficient was used to generate dendrograms from gel banding patterns. A Dice coefficient >70% indicated similarity or match among PFGE genotypes. Results: In 26% (7/27) of mother/child pairs, all of the child's isolates matched the mother. In 15% (4/27), some of the child's genotypes matched the mother, and in 59% (16/27), no isolates matched the mother. Maternal transmission was a mode of MS acquisition in 41% (11/27) of mother/child pairs, while acquisition from non-maternal sources occurred in 74% (20/27). Conclusions: MS genotypes that did not match maternal strains were identified in the majority of children (74%) within this S-ECC population. Evidence of maternal transmission was detected in 41% of mother/child pairs.