The Northeastern Gulf of Mexico Physical Oceanography Program (NEGOM) is supported by the Minerals Management Service (MMS) of the U.S. Department of the Interior. Through a contract between MMS and the Texas A&M Research Foundation, several components of the Texas A&M University System are conducting the Chemical Oceanography and Hydrography study of NEGOM (NEGOM-COH). This report covers activities from October 1997 through June 1998. Data were collected from hydrographic and acoustic Doppler current profiler (ADCP) surveys conducted in the Gulf of Mexico over the continental shelf and upper slope between the Mississippi delta and Tampa Bay in water depths of 10 to 1000 m. Additionally, historical and concurrent data from other programs in this region were collected. Two hydrographic/ADCP surveys, N1 and N2, were conducted with 94 and 98 hydrographic sampling stations and with 80 and 97 expendable bathythermograph stations on respective cruises. Each survey also included continuous ADCP measurements along the cruise track. At each hydrographic sampling station continuous profiles were made of conductivity, temperature, pressure, downwelling irradiance, fluorescence, and light transmission. Up to twelve water samples were taken at each station and analyzed for dissolved oxygen and six nutrients: nitrate, nitrite, phosphate, silicate, ammonium, and urea. At 51 stations on cruise N1 and 61 on N2, water samples were filtered and analyzed for phytoplankton pigments at the surface and from the chlorophyll maximum and the low light regime immediately below it. Pigments were determined using high performance liquid chromatography. At 60 stations on each cruise, water samples were filtered and analyzed for particulate matter concentrations at surface, middle, and bottom water depths and for particulate organic carbon concentrations at surface and bottom water depths. Bottle salinity was measured at every station on the first cruise and at the shallowest and deepest stations on each cross-shelf line on the second. The instrumentation as well as calibration and sampling procedures are described in this report. The collected data were subjected to stringent quality assurance/quality control procedures.