Insect cell culture has become increasingly useful for the production of heterologous proteins as well as of baculovirus polyhedra, and several different culture media formulations can be employed for this purpose. The goal of this work was to assess the potential of lyophylized milk whey ultra filtration retentate (MWR) when associated to yeast extract (YE), glucose and Pluronic F68 (PF68) to partially replace fetal calf serum (FBS) in Spodoptera frugiperda Sf9 cells culture in Grace's medium, aiming AgMNPV baculovirus production. Batch cultivation results showed that the yeast extract and the milk whey concentrate effectively increased cell concentration to about half the level commonly verified for the Sf900II serum-free medium. A 4-fold increase in viable cell concentration was achieved when employing 5% (w/v) MWR, 8 g/L YE, 1% (v/v) of FBS and 2.7 g.l-1 of glucose, resulting in 1.6 x 10(7) polyhedra.ml-1 after infection with baculovirus.