We have adapted the Syva Emit® gentamicin and tobramycin procedure to the IL microcentrifugal analyzer, MCA III®. With this instrument the recommended instructions for reagent preparation and reaction sequence did not produce a useable standard curve. We modified the dilutions and volumes for the working reagents and reversed the sequence of addition of the working reagents. We assessed the linearity and precision of the analysis and compared the Syva gentamicin and tobramycin Emit procedure on the IL MCA III with the semiautomated procedure on a Gilford Stasar III spectrophotometer. With the IL MCA III® only 3 to 5μ of serum is used, 17 analyses can be obtained in 8 min, and the reagent costs are reduced considerably.