In two crossover studies with 12 (6 males/6 females) healthy young volunteers each, we compared the bioavailability of Neoimmun capsules with the microemulsion Neoral and the influence of a fat-rich breakfast on the bioavailability of Neoimmun. Each volunteer received a single dose of 200 mg cyclosporine A in each period. Blood samples were taken up to 24 h and analysed for cyclosporine A by high-performance liquid chromatography (HPLC) and photometric detection. The pharmacokinetic parameters were determined by non-compartmental analysis. The treatments were tested for bioequivalence and significant differences. The bioavailability of Neoimmun was significantly lower compared to Neoral, albeit Neoimmun met the bioequivalence criterion (90% confidence interval of AUC 0.80-0.94) or missed the criterion only marginally (90% confidence interval of c(max) 0.75-0.91). The bioavailability of Neoimmun as determined by area under the blood concentration-time curve (AUC) increased by nearly 20% after a fat-rich breakfast. However, mean peak concentrations after food were only higher in male subjects, whereas mean peak concentrations in female subjects were lower compared to fasting administration. In conclusion, our data show that Neoimmun exhibits a lower bioavailability than the microemulsion Neoral and that food has a significant but variable and sex-dependent impact on the bioavailability of Neoimmun capsules.