Compliance with the NAAQS for ozone will require the reduction of non-methane organic carbon (NMOC). To this end speciated hydrocarbons were determined for over 800 ambient air samples from 39 U.S. cities from 1984-1986. Samples were collected in stainless steel spheres on week days from 6 to 9 a.m. during June through September. C2 to C12 hydrocarbons were determined by capillary GC/FID with sample cryogenic preconcentration. The GC retention time identification table consisted of 314 uniquely numbered peaks, of which 97 were specifically named, 214 were identified by type (olefin, paraffin, aromatic). GC-MSD/FID analysis confirmed the identity of 40 peaks and indicated the presence of oxygenated, chlorinated, and fluorinated hydrocarbons in some samples.