An ultrahigh vacuum compatible methyl radical source has been developed and characterized. The methyl radicals were generated by passing a dilute mixture of methane in argon through a microwave discharge and sampling the discharge products using a molecular beam skimmer. The resulting molecular beam was characterized using a differentially pumped mass spectrometer. In addition to methyl radicals, other species observed in the beam included methane and higher hydrocarbons whose relative amounts were affected by source operating conditions. Radical fluxes as high as 8.4 x 10(14) cm(-2) s(-1) were produced. (c) 2006 American Vacuum Society.