The effects of 22 organic solvents were tested on the bioconversion of (R)-(+)-limonene to (R)-(+)-alpha-terpineol by free and immobilized P. digitatum mycelia. Free cells showed the highest bioconversion activity in water-organic co-solvent single-phase systems. The relative activity increased 2.4 fold with dioctylphthalate (1.5%, v/v) and 2.2 fold with ethyl decanoate (1.5%, v/v). Immobilized cells showed the greatest bioconversion in detergent reversed micelle systems. When Tween 80 (0.1%) or Triton 100-X (0.1%) was added into an immobilized P. digitatum bioconversion system, the relative bioconversion activity increased 2 fold. Immobilization protected the fungal cells from the cytotoxic effects of organic solvents. Dioctylphthalate 1.5% to 2% (v/v) was the optimum concentration range for free cell bioconversion, and Tween 80 0.5% to 1% (v/v) was the optimum concentration range for immobilized cell bioconversion.