Multitube collimators driven at low pressure, usually 1 Torr or less, have been extensively used up to now to produce collimated molecular beams. We have found experimentally that such devices, when driven at high pressure, 1<P0<100 Torr, lose almost completely their collimation properties. However, they produce a sensible cooling of the gas in the beam at a density high enough to make the high‐pressure regime attractive for molecular spectroscopy. Moreover, we have observed for the first time an oscillatory behavior of the angular spread of the beam versus the pressure.