In a wind-tunnel study, recorded video images of the top view of smoke dispersion in the wake of a building were analyzed. A continuous source of smoke was emitted at floor level, midway along the leeward side of the building. The technique and usefulness of analyzing video images of smoke is demonstrated in a study of building effects on smoke dispersion. The presentation discusses how the video image intensity is corrected for background intensity and then normalized to a scale of 0 to 100 percent. Profiles of the normalized image mean intensity are compared with similar profiles for the mean concentration of hydrocarbon tracer. The distributions of intensity of cross-stream profiles are discussed. These distributions were analyzed in time and space. Also, time-averaged cross-stream profiles of mean, standard deviation, and other statistics of image intensity are compared with traditional concentration measurements for symmetric wake flow.