The biology of Amphitetranychus viennensis was studied on black cherry (Prunus serotina) trees in an orchard in Baraghan in 2002,and also under laboratory conditions at 23 deg. C, 75% relative humidity, and a 16L:8D. Females of the mite began their activities near the end of May and produced 3 generations per year. In the laboratory, the mean time for development from egg to egg was 16.18 and 11.93 days for females and males, respectively. The average pre-oviposition, oviposition and post-oviposition periods were 2.25, 4.91 and 1.12 days, respectively.