The big bud mites Phytoptus avellanae Nal. and Cecidophyopsis vermifomis Nal. cause significant yield loss in hazelnut (Corylus avellana L.) orchards. Determination of effective pesticides and the proper timing of their application against big bud mites were studied in the Samsun province of Turkey. Two field trials were conducted from 1994 to 1997. The migration period of the mites (April-May) was covered each year. Nine pesticides (Sulphur WP, Azinphos-methyl EC, Azinphos-methyl WP, Dimethoate EC, Bromopropylate EC, Amitraz EC, Quinomethionate WP, Carbosulfan EC and Methidathion EC) were evaluated at their registered application rates as alternatives to the standard pesticide Endosulfan EC. Sulphur 80% WP was as effective (83.25%) as Endosulfan 35% EC (83.35%) for the control of big bud mites. A single application of Sulphur 80% WP (400 g/100 L) at the end of April or beginning of May, just before the peak period of mite migration from old big buds to new buds, was very effective in keeping mite and big bud numbers low.