The microwave spectrum of trans-nitrosoethylene-15N (nitrosoethene) generated by pyrolysis of chloroacetaldehyde oxime-15N has been observed in the frequency range from 8.0 to 40.0 GHz. The relational constants of the 15N species are determined to be A= 50390 (201), B= 5057.00 (3), and C= 4605.29 (3) MHz. The rs-coordinates (a and b) of the nitrogen atom of trans-nitrosoethylene are determined to be 0.540 (1) and 0.453 Å, respectively. ...