The growth in number and kind of online reference services has resulted in both new users consulting library research services as well as new patterns of service use. Staffing in-person and virtual reference services desks adequately requires a systematic analysis of patterns of use across service points in order to successfully meet fluctuating patron needs. This article examines an assessment methodology for examining patron use of in-person and virtual reference services, and designing variable staffing models which balance the observed needs of each mode of communication and patron type. (Contains 5 figures and 6 tables.)