This study applied functional analysis methodology to nail biting exhibited by a 24-year-old female graduate student. Results from the brief functional analysis indicated variability in nail biting across assessment conditions. Functional analysis data were then used to guide treatment development and implementation. Treatment included a simplified habit reversal package that was modified based on results of the functional analysis. Following treatment implementation, nail biting decreased as evidenced by consistent nail growth and participant self-recorded data. Results are discussed in terms of treatment utility of functional analysis methodology for novel populations and response topographies. (Contains 4 figures.)