The IRAM 350 GHz SIS receiver has been installed and used during the week from 4 to 11 of March, with exellent results. The receiver performance was very good, with receiver noise temperatures of 70 K to 100 K on the sky (including optics) and a sideband rejection of about 6 dB. The weather was excellent during a large fraction of the time. System noise temperatures of 400 K to 600 K at 350 GHz were not unusual, even during daytime ! These low temperatures correspond to about 0.5 mm of precipitable water vapour, clearly demonstrating the potential of the 30m telescope site for observations at 0.8 mm wavelength.