In the aim of beta-carotene biocompatible extraction, toxicity of various pure solvents belonging to different homologous series has been investigated for Dunaliella salina. The results showed that solvents having logP(oct) > 5 or having a molecular weight over 150 g/mol can be considered biocompatible for this microalga. The membrane critical solvent concentration for each series of solvents has been calculated applying Osborne's model, showing that the aliphatic chlorinated hydrocarbon is the most toxic family studied. Mixtures of a biocompatible solvent (decane) with a toxic solvent (CH(2)Cl(2), MEK, MTBE) have been studied. The beta-carotene extraction ability of CH(2)Cl(2)-decane mixture was found six times more efficient than with pure decane. It has been demonstrated that the extraction ability of solvent depends on its affinity with the product extracted and on its concentration incorporated in the cellular membrane.