In this preliminary report of a 20-week trial, 66 patients with non-insulin-dependent diabetes mellitus (NIDDM) and hyperlipidaemia who remained eligible after an 8-week dietary stabilization phase were randomly allocated to receive 20 mg of fluvastatin or placebo once daily for 6 weeks. Fluvastatin was subsequently increased to 20 mg twice daily and administered according to the same schedule, versus placebo, for a further 6 weeks. Both dosages of fluvastatin substantially improved serum lipid profiles compared with baseline and placebo. Both dosages of fluvastatin significantly reduced low-density- and very-low-density-lipoprotein (LDL, VLDL), cholesterol and triglyceride (TG) compared with placebo, and both dosages significantly elevated high-density-lipoprotein (HDL) cholesterol. The ratio of LDL to HDL was also significantly decreased. Amongst the 58 patients who completed the study, there was no evidence either of myopathy or of hepatotoxicity; mean creatine kinase values remained stable in the fluvastatin arm. Fasting glucose, glycosylated haemoglobin, and fructosamine levels were not markedly affected by active treatment. No serious adverse events attributable to the drug were reported. In conclusion, both dosages of fluvastatin appear to be effective and safe in the management of hyperlipidaemia in this outpatient, maturity-onset, diabetic population.