A resin composition comprising a polyphenylene ether produced by polymerizing a monomer component consisting of 100 parts by weight of 2,6-dimethylphenol and 0.5 to 7.5 parts by weight of o-cresol in the presence of both a catalyst and an oxygen-containing gas and a flame retardant. When the polyphenylene ether has a molecular weight distribution of 2.8 to 8.0, the resulting resin composition is more excellent in flame retardance, particularly anti-dripping properties in burning. The resin composition is applicable to not only electric and electronic applications necessitating high flame retardance but also other fields of application of polyphenylene ether resins.