The paper gives preliminary results of measurements of hydrocarbon emissions from a number of petroleum refineries. Sampled sources included valves, flanges, pump and compressor seals, pressure relief devices, drains, and cooling towers. The paper discusses sampling techniques and describes the analyses and correlation of the sampling data. Data obtained to date supported the following conclusions: (1) Emissions form flanges are not significant. (2) Compressor seals have the highest average leak rate of the baggable sources. (3) Valves contribute more emissions than any other single baggable source. (4) Most leakage occurs from a relatively few sources of each source type. (5) The type of process stream has a substantial effect on the source emissions. (6) Losses from cooling towers are quite low.