To ascertain if nail biting (usually considered a manifestation of emotional tension) was associated with fibromyalgia, 387 patients attending the Rheumatism Clinic at the Leeds General Infirmary were studied prospectively. Bitten nails appeared to be a feature of youth rather than of fibromyalgia. Patients with a full set of dentures were less likely to bite their nails than others, but it can and was done by 7%. Posing the question about nail biting worried several patients, indicating the wisdom of seeking ethical approval even for "noninvasive" studies.