The millimeter-wave spectrum of AlNC (X 1Σ +) has been recorded using direct absorption techniques in the range 131-536 GHz, including data for several quanta of the bending vibration and the 13C,isotopomer. The species was created by the reaction of aluminum vapor and trimethylsilyl cyanide. Twenty rotational transitions were recorded for the main isotopomer and nine for AlN 13C, as well as lines for the (01 10), (02 0o) states. Rotational and l-type doubling constants have been determined for this species, as well as bond lengths. These measurements indicate that AlNC is a linear and fairly rigid molecule, as well as being the favored isomer, in agreement with theory.