A shore-based team observed humpback whale behavior and movements before, during, and after a playback of the ATOC m-sequence. Eighty-four trials were conducted with both ATOC and no-sound control conditions. Shore observers did not know which sound condition was used. Playbacks originated from a projector suspended beneath a moored boat. The source level was 172 dB re: 1 (mu)Pa (60- to 90-Hz band). A second drifting vessel measured received levels and ambient noise. Received levels were measured between 105 and 130 dB. No overt responses were noted during the experiment. Movement and behavioral variables were examined for changes due to playback. Comparison of whale tracks between control and experimental conditions showed no difference in distribution. Preliminary analysis of the data found no changes in the movement variables and a slight change in respiratory behavior. Whales appear to have longer surface intervals during playback then during control trials. The magnitude of this effect on humpbacks appears to be comparable to effect of small vessels.