Only with ArcInfo license:Project both feature classes to the same projected coordinate system so that a linear measurement is meaningful. Apply any datum transformations necessary.Run Analysis Tools -> Proximity -> Near, specifying a search radius that will be sure to return a match for every record of the Input Features. Enable the "Location" option to add the distance, FID, x, and y coordinates of the closest "Near" feature to the Input features. The FID of the closest Near feature is now in the attribute table for each Input record. Perform an attribute join of Input features with Near features using the NEAR_FID field in the Input layer and the FID in the Near layer. This adds the attributes of the nearest point in Near to the records of Input.