Microscopic litter particles in waste water from three waste water treatment plants (WWTPs), VEAS (700 000 population equivalents, pe), Tönsberg (185 000 pe) and Fuglevik (85 000 pe) were studied. Samples were taken by filtration of influent and effluent waste water, and also from the water right before the biological treatment at VEAS. The filters were analysed with stereomicroscopy, and the microlitter particles counted and categorized. To compare particles of different size classes, filters with two different mesh sizes were applied: 300 µm and 20 µm. It should be emphasized that particles that are collected on a 20 µm-filter will of course include also the size of particles that are collected on a particles ?300 µm filter. The analysed particles were divided into two main categories: microplastics and non-synthetic anthropogenic fibres (in the report referred to as non-synthetic fibres ). The latter category included e.g. cotton fibres from clothes. The study was based on a limited amount of data; only two samples were taken from influent and two from effluent water at each WWTP. So caution should be taken when interpreting the results. Still, valuable information on the importance of the WWTPs as gateways for microlitter to the environment has been obtained.