This study has been carried out in response to the request of Zbrojovka A. S. Vsetin, a producer of weaving looms. The firm, decided, in collaboration with the Department of Weaving Technology of the Technical University in Liberec, to start a research programme studying the effect of dynamics of the high speed weaving process on the quality of produced fabric and on the stability of fabric formation. This paper deals with a particular problem of this programme - with the possibilities and causes of the occurrence of weft bariness in fabric on weaving machines at high weaving speeds.