  We report the first detection of a Sunyaev-Zel'dovich (S-Z) decrement with
the Arcminute Microkelvin Imager (AMI). We have made commissioning observations
towards the cluster A1914 and have measured an integrated flux density of -8.61
mJy in a uv-tapered map with noise level 0.19 mJy/beam. We find that the
spectrum of the decrement, measured in the six channels between 13.5-18GHz, is
consistent with that expected for a S-Z effect. The sensitivity of the
telescope is consistent with the figures used in our simulations of cluster
surveys with AMI.
