Particles of tread rubber debris produced by laboratory wear tests are imaged by light microscopy. The fractal dimension, DF
, of the image perimeter is estimated. The sensitivity of DF with respect to the image acquisition and processing parameters is determined. Particles belonging to two types of undifferentiated debris, low severity (LS) and rasping (R), respectively, are analyzed. The values of DF
have distributions, which, if suitably interpreted, allow the identification of either debris type with the following conditional probabilities: pLS|LS
= 0.71 and pR|R
= 0.81. The procedure can be eventually applied to environmental impact studies.