A new uniplanar CPW-slot double junction balun has been proposed. Being realised as a uniplanar equivalent of the microstrip-slot double junction transition, this balun is well suited for MMICs, and has better characteristics than other uniplanar baluns published up to now. The measured VSWR is less than 1.6 and insertion loss is about 0.7 dB for band-width ratio 1:6.