This data set contains Vegetation and Site Characterization data from the 1998-99 ATLAS Grid Transect, Northern Alaska. This data set comprises the text and data presented in the data report "A western Alaskan transect to examine interactions of climate, substrate, vegetation, and spectral reflectance: ATLAS grids and transects, 1998-1999." The report is a compilation of data from two projects conducted on the North Slope of Alaska during the summers of 1998 and 1999. The first project involves environmental, climate, soil, vegetation, and remote-sensing data collected from 8 ATLAS (Arctic Transitions in the Land-Atmosphere System) grids established along a North-South transect from Barrow to Ivotuk, Alaska. The original purposes of the study were (1) to characterize the major zonal vegetation types found along the North Slope climate gradient, (2) to quantify differences between acidic and non-acidic tundra along the same gradient, and (3) to investigate relationships between plant biomass, Leaf Area Index (LAI), and Normalized Difference Vegetation Index (NDVI). This part also includes a brief analysis of interactions between plant functional type composition, LAI, NDVI, and summer temperature. This analysis is limited to moist acidic tundra (MAT) and moist non-acidic tundra (MNT) comparisons using data from six of the eight grids that best represent acidic and non-acidic mesic vegetation. The second project is an accuracy assessment of a Landsat MSS-derived landcover map of northern Alaska, which involved creating several large transects over northwest Alaska. Included here is a table of LAI measurements from eight random points along these transects, as well as the accompanying releve and site factor data sheets. No analysis of these data is presented.