We present an example of background statistics in studies of fluctuating asymmetry (FA); calculations of asymmetry, measurement error (ME), and repeatability. Nine bilateral metric traits in skulls and lower jaws of 691 East Greenland and Svalbard polar bears (Ursus maritimus) were measured twice, and examined for asymmetry. The skulls were collected in the period 1892–2004. In this study, 2.0% of the FA data were identified and treated as outliers, which is less than in comparable studies. FA for each trait amounted to 0.1%–3% of the average size of the corresponding trait. The magnitude of FA generally increased with trait size. For every trait measured, ME was found to be smaller than FA. The repeatability of the traits was inversely proportional to ME. Five of the nine traits had a repeatability of 90% or more, which is similar to what has been reported in other studies.