An alternative to automated testing is the use of E-test strips (AB Biodisk). E-tests are strips with increasing concentration of the particular antimicrobial agent from one pole to another which when applied to a plate of bacterial isolates produces a tear-drop shaped area of killing, with greater killing toward the end with the greater concentration (Figure). Though more cumbersome and expensive than automated testing, an accurate assessment of the presence or absence of heteroresistance and the more precise determination of MIC's are possible with E-tests compared to automated testing. Determination of prevalence of MRSA heteroresistance to vancomycin and relationship between E-test and automated vancomycin MIC's for MRSA are primary objectives of this investigation.