Post-mortem biochemical analyses of dog lenses and of aqueous humour of a 2 year oral toxicity study in the dog with Fluvastatin (control, 1, 8 and 16 mg/kg/day) did not show any relationship to the observed lens opacities (3 animals out of 8 at 16 mg/kg/day). With respect to lens transparency, a daily dosage of 8 mg/kg/day Fluvastatin to dogs over a period of 2 years is non-cataractogenic. Mean data on lenticular enzyme activities (GPX, G6PH, GAPDH, ALD, AR, LDH, PFK and SDH) as well as measurements of GSH/GSSG, ATP, ADP, AMP, Gluc, Fruc, Sorb, G6P and F6P do not indicate changes which may directly lead to lens opacifications. Conformational changes of lens proteins (heat lability of PFK-activity), a shift in the albumin/IgG ratio of aqueous humour and equatorial lens protein composition changes (after isoelectrofocusing) were observed. The biological significance of these changes is unknown as the non-cataractogenic dose for lens opacities in beagle dogs is 8 mg/kg/day.