Enzymatic degradation of a model polyester was studied under varying conditions. Poly(trimethylene succinate) was hydrolyzed by the use of lipase from Rhizopus delemar. An enzyme assay was adjusted for the use of insoluble substrates and gave well-reproducible data. Ester bond cleavage was measured with respect to time. Comparison of ester cleavage and weight loss-a commonly used technique in the evaluation of polymer biodegradation-indicated that oligomers with an average length of five to sin monomers are released from polymer bulk. Thus, weight loss as well as dissolved organic carbon measurements will not give information on real enzymatic degradation activity, because solubility properties of oligomers are superimposed. Time-dependent degradation profiles are strongly influenced by the materials surface (film or polydispers powder) as well as the addition of surfactants. The use of Triton X-45 did not assist the degradation of the insoluble substrate, as it did with commonly applied emulsions of liquid substrates. On the contrary, at concentrations above 0.5% (vol/vol), the addition of Triton X-45 inhibited enzymatic degradation to a great extent.