Little is known about the sounds produced by the Sei Whale Balaenoptera borealis and no recordings have been made in their presence in the Pacific Ocean. This research presents sounds recorded in the presence of Sei whales near the Hawaiian Islands in November, 2002. A total of 107 vocalizations, including two variations of low-frequency downswept calls, were measured. Two of these calls were sweeps from100 Hz to 44 Hz, over 1.0 seconds. The second call type (n=105) consisted of low frequency calls which swept from 39 Hz to 21 Hz over 1.3 seconds. These calls are different from sounds attributed to Sei whales in the Atlantic and Southern Oceans, where recordings were made only in the summer months. These sounds are similar, however, to sounds attributed to fin whales in Hawaiian waters. Additional studies are needed in order to understand the spatial and temporal variation in the vocal repertoire of Sei and Fin whales in the Pacific Ocean.