Visitor behavior research has become an essential component to many museum programs. Since its opening to the public in 1965, Oregon State University's Mark O. Hatfield Marine Science Center Aquarium in Newport, it has been visited by millions of people. A clear understanding of who this audience was and what they actually did while viewing the exhibits in the aquarium had never been achieved. This descriptive study describes fall season visitors and their circulation patterns. The goal of the study was to understand the interrelationships between visitors, exhibits and the physical layout of the aquarium. One purpose of the study was to provide information that would aid staff members with long range planning decisions that include the design of new exhibits and the renovation of older displays. Besides identifying the aquarium's fall audience, demographic data on visitors was desired to gain a clearer understanding of populations that did not visit the museum. Two-hundred and forty participants responded to a survey questionnaire administered by HMSC volunteers and the author. Forty unobtrusive observations of visitors were collected by the author. Respondents included all age groups; however, the young adults (late teens, early twenties) were underrepresented. Over half of the respondents had visited HMSC before; 81% of repeat visitors were from Oregon. A positive correlation was shown to exist between group size and the length of visit. The larger the group the longer the group tended to visit in the aquarium. The average time spent in the aquarium was 30.6 minutes. Most (82.5%) respondents overestimated the length of their visit by an average of 22 minutes. Overall, visitors were found to spend over 77% of their time at HMSC viewing the exhibits. Only 7.3% of the visitors observed traveled through the aquarium the way it was designed. The average amount of time spent at exhibits ranged from 16.6 seconds to 212.5 seconds; however, standard deviation and range indicate a great deal of variability in visitor behavior. Visitor traffic patterns and competition between exhibits was shown to influence the visitor experience. Survey and observation results were consistent with examples at other museums, zoos and aquariums cited in the literature. / Graduation date: 1992