A filter device having filter means, in particular hollow-fibre membranes, arranged in more than one filtration compartment within a filter housing. The filter device thereby allows more than one filtration process to be carried out serially and/or simultaneously within a single housing. For example a dialysis type filtration process such as haemofiltration or haemodiafiltration or haemodialysis may be carried out at the same time as an ultrafiltration process or as another haemofiltration, haemodiafiltration or haemodialysis process. The device may have a split shell construction bonded or welded together along longitudinal seams. Internal separating walls within the housing are formed integrally with the shell portions of the housing to form adjacent filtration compartments when the housing portions are joined together.
