Optimal design and operation of bioreactors for insect cell culture is facilitated by functional relations providing quantitative information on cellular metabolite consumption kinetics, as well as on the specific cell growth rates (mu(G)). Initial specific consumption rates of glucose, malate, and oxygen, and associated changes in mu(G). Were measured for Spodoptera frugiperda clone 9 (Sf9) cells grown in batch suspension culture in medium containing 7-35 mM glucose, 0-16 mM malate, and 4-16 mM glutamine. The initial specific glucose consumption rate (q(G)) could be described by a modified Michaelis-Menten equation treating malate as a "competitive" inhibitor (K-I = 6.5 mM) and glutamine as a "noncompetitive" inhibitor (K-I = 14 mM) of q(G), with a K-m of 7.1 mM for glucose. All three carbon sources were found to increase mu(G) in a saturable manner, and a modified Monod equation was employed to describe this relationship (mu(Gmax) = 0.047 h(-1)). The initial specific oxygen consumption rate (q(O2)) in Sf9 cells could be related to mu(G) by the maintenance energy model, and it was calculated that, under typical culture conditions, about 15-20% of the cellular energy demand comes from functions not related to growth. Fitted parameters in mathematical expression for mu(G) : K-4, Monod constant for glucose (mM); K-5, modified Monod constant for malate (mM); K-6, Monod constant for glutamine (mM); m(O2), specific consumption rate of oxygen by the cells under zero-growth conditions (nmol/cell/h); q(F), initial specific fumarate production rate (nmol/cell/h); q(G), initial specific glucose consumption rate (nmol/cell/h); q(Gmax), maximum initial specific glucose consumption rate (nmol/cell/h); q(M), initial specific malate consumption rate (nmol/cell/h); q(O2) initial specific oxygen consumption rate (nmol/cell/h); Y-O2, cell yield on oxygen (cells/nmol); mu, initial specific cell growth rate (h(-1)); mu(G), initial specific cell growth rate (h(-1)); mu(Gmax), maximum initial specific cell growth rate (h(-1)).