Results from an 'acid rain' field study around the city of Philadelphia are presented. The study involved the sampling of wet deposition at a network of 40 sites within a distance of 60 km from the Delaware River. Emphasis was placed on event-type rain sampling of frontal and primarily nonconvective storms which are responsible for most of the Northeast's wet deposition. For most storms, meteorological conditions contributed to a predominant southeasterly transport. Since most of the area's urban and industrial emissions occur along the Delaware River, the Pennsylvania sector of the network was identified as the downwind (target) region; the New Jersey sector was the upwind (control) region. (Copyright (c) 1985 - Air Pollution Control Association.)