The marine transfer emission factors documented in the American Petroleum Institute (API) publication entitled 'Atmospheric Hydrocarbon Emissions from Marine Vessel Transfer Operations, API 2514A' (API, 1987) has been widely accepted by industry and by the Environmental Protection Agency (EPA) as containing accurate equations to calculate emissions from marine transfer operations. However, recent emission testing of crude oil loading operations at Valdez, Alaska, by the Alyeska Pipeline Service Company, together with its owner company organizations, Atlantic Richfield (ARCO), British Petroleum (BP), and EXXON, indicated higher crude oil loading emissions than that predicted by the API equations in API 2514A (Alyeska, 1990). As a result of this, and a part of the API 2514A reaffirmation process, API retained CH2M HILL to assess the validity of the API 2514A marine vessel loading equations in light of this new Alyeska data and any additional data available in literature and from API members, and to make specific recommendations for improving the validity of API 2514A. Although the evaluation of crude oil loading emissions is the main emphasis of this study, a review and critique of the gasoline loading and crude oil ballasting emission factors and equations in API 2514A was also performed. This report is divided into five major sections: 1. A summary of the results of a literature search of published information and a telephone survey of unpublished information from API member organizations on marine vessel loading and ballasting emissions (First part of Task 1, Section 3 of the report). 2. A review and critique of the crude oil loading, gasoline loading, and crude oil ballasting emission test data bases and associated emission models (Second part of Task 1, Section 4 of the report). 3. A direct comparison of measured and predicted emissions from marine vessel loading and ballasting operations (Task 2, Section 5 of the report). 4. An assessment of the validity and application of API emission estimates in light of new test data and the reviews summarized in Sections 3 through 5 (Task 3, Section 6 of the report). 5. Specific recommendations on improving the validity and application of API 2514A emission estimates (Task 4, Section 7 of the report).