Batch experiments were conducted to compare the waste water treatment efficiencies of plant-free microbial filters with filters supporting the growth of reeds (Phragmites communis), cattail (Typha latifolia), rush (Juncus effusus), and bamboo (Bambusa multiplex). The experimental systems consisted of two components in series. The first component was an anaerobic settling-digestion container. The second was a 'non-aerated' trough filled with rocks, decreasing from large rocks (up to 7.5-cm diam) at the bottom, to pea gravel (0.25- to 1.3-cm diam) at the top. The plant-free microbial filter was equally effective in carbonaceous BOD removal. The vascular aquatic plant series enhanced ammonia removal, and consequently improved nitrogenous BOD5 removal. Under the conditions of these experiments, raw sewage with initial BOD5's of 100 mg/l can be upgraded to meet secondary standards.