A coaxial-cable capacitive-loaded interstitial antenna (CCIA) is proposed for 2.45 GHz. The capacitive load contributes to almost perfect matching and desirable heating area. The measured return loss of the CCIA is -28.377 dB, which may be considered as the best among those reported. Owing to this excellent result, the CCIA can also be applied for treatment of deep-seated tumours or cancer.