This study investigated the influence of several factors on the redistribution of extraneous textile fibres on garments during machine washing. Cotton T-shirts were seeded with known numbers of acrylic, wool and viscose target fibres in controlled positions and laundered in top-and front-loading machines, both individually and accompanied by undergarments. The persistence of target fibres was low (generally 510%), but never zero. Between 50% and 100% of recovered fibres were redistributed away from the primary contact area. A secondary transfer of target fibres always occurred to at least one undergarment, 90% of experiments resulting in fibres transferred to the inside surface of the undergarments. This implies that whilst valuable fibre evidence may be recovered from garments after machine washing, the location of recovered fibres should not be relied upon to corroborate alleged scenarios when it is known or suspected that the garment under investigation has been laundered.