Engineering practice in trickling filter design has been influenced by the propagation of myths as much as by the analysis of data and factual determinations. In this paper, several common myths encountered by the writer in his engineering practice are examined. The myths are tied to source(s) where possible, and then the factual underpinnings (if any) are examined. Common myths include the following: (1) Trickling filter processes are less reliable than activated sludge processes; (2) trickling filters are poor performers in cold weather; (3) trickling filters are more expensive; (4) motorized distributor speed control is always needed; (5) cross-flow media should not be used at total organic loadings exceeding 1.6 kg BOD/m3 – d and (6) all media are created equal.