This work describes the construction and evaluation of lactate sol-gel biosensors to accomplish the determination of lactate in pharmaceutical products. Lactate oxidase was incorporated in a porous sol-gel film placed onto a platinum-based electrode. Acid and basic catalysis were assessed. When coupled to a sequential injection system (SIA) the biosensor, based on (3-aminopropyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, deionised water, polyethylene glycol 6000 and acid catalyst, presented a range of linearity of 5 x 10(-5) to 5 x 10(-3) M. The analytical usefulness of the developed biosensor was evaluated through analysis of commercial pharmaceutical products containing lactate with a sampling rate of 40 samples h(-1). The enzyme remained active for at least 30 days, enabling about 700 determinations without sensitivity decrease. (c) 2006 Elsevier B.V. All rights reserved.