In this communication we report high performance gain characteristics measured at T=77K in electron injected MW HgCdTe APDs. A full set of characterisations, including gain, excess noise, dark current and first measurement of the impulse response, was performed on test arrays of backside illuminated pin type MW APDs, manufactured at CEA LETI using an MBE grown HgCdTe absorption layer. A record high avalanche gain of M=5300 have been demonstrated in these diodes, associated with a low noise factor, F=1.0-1.3, and low dark current. The sensistivity of the APD is discussed in terms of the impact of the distribution of the gain in the structure for different applications and we have estimated a shot noise equivalent input current, Ieq_in=2.0 10-13 to 1.0 10-12A, for continuous measurements, and a dark count rate for photon counting applications DCR=2.7 106 s-1. The first measurements of the impulse response of the MW HgCdTe APDs showed that the band width was only weakly dependent on the gain, in coherence with the dominant electron multiplication evidenced by the low value of the noise factor. At the maximum gain, M=5000, we measured a risetime of t10-90=88ps and a fall time of t90-10=2.4ns, yielding a record high band width product of GBW=723GHz (BW=145MHz), mainly limited by the diffusion and life time of the minority electrons.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.