Pilot-scale rock filters were constructed at the outlet of a large waste stabilization pond facility in Jordan. Their viability in upgrading the ponds' effluent was studied over a period of eleven months. This was done through studying the efficiency of four different types of locally available inexpensive materials placed in six filters and configured in three trains. The efficiency of each filter and the three combinations was evaluated. Results show that the filters can reduce the ponds' effluent content of TSS and BOD5 by 60%, TFCC by a maximum of 94% and T-P by 46%. This was achieved with a loading of 0.033-0.044 kgTSS/m3.d at an average temperature of 25 °C. Of the four media, the wadi gravel medium (3-23 cm) performed best. It was concluded that rock filters constitute a promising upgrading technique for pond effluent.