A brief investigation was made to determine the quantities of spent, mixed-waste HEPA filters within the DOE Complex. The quantities of both the mixed-waste filters that are currently being generated, as well as the legacy mixed-waste filters being stored and awaiting disposition were evaluated. Seven DOE sites representing over 89% of the recent HEPA filter usage were identified. These sites were then contacted to determine the number of these filters that were likely destined to become mixed waste and to survey the legacy-filter quantities. Inquiries into the disposition plans for the filters were also made. It was determined that the seven sites surveyed possess approximately 500 m3 of legacy mixed-waste HEPA filters that will require processing, with an annual generation rate of approximately 25 m3. No attempt was made to extrapolate the results of this survey to the entire DOE Complex. These results were simply considered to be the lower bound of the totality of mixed-waste HEPA filters throughout the Complex. The quantities determined encourage the development of new treatment technologies for these filters, and provide initial data on which an appropriate capacity for a treatment process may be based.