The lack of instruments available for the measurement of fine dexterity (i.e., speed of interdigital manipulation) implies a gap not only in the occupational therapist’s ability to quantify and deal precisely with patients’ problems in this area, but also in the knowledge base of occupational therapy itself. The Rosenbusch Test of Finger Dexterity (developed by Doris F. Rosenbusch, MA, OTR), a new instrument that measures the speed of interdigital manipulation of objects by each hand separately, was tested on 64 subjects with normal hand function and 10 subjects known to have disabilities affecting fine dexterity. The determination of significant differences by the subjects’ sex, dominant and nondominant hands, and normal and dysfunctional hands was performed with t tests. The scores of the subjects with normal hand function versus those with disabled hand function were then compared on all variables. The findings demonstrate that this instrument is ready to be used experimentally and compares favorably with current commercial tests on both reliability and validity coefficients.