Biologic agent screening is a three-step process: lysis of host cell membranes or walls to release their DNA, polymerase chain reaction to amplify the genetic material and screening for distinguishing genetic signatures. Macrofluidic devices commonly use sonication as a lysis method. Here, we present a piezoelectric microfluidic minisonicator and test its performance. Eukaryotic human leukemia HL-60 cells and Bacillus subtilis bacterial spores were lysed as they passed through a microfluidic channel at 50 microL/min and 5 microL/min, respectively, in the absence of any chemical denaturants, enzymes or microparticles. We used fluorescence-activated cell sorting and hematocytometry to measure 80% lysis of HL-60 cells after 3 s of sonication. Real-time polymerase chain reaction indicated 50% lysis of B. subtilis spores with 30 s of sonication. Advantages of the minisonicator over macrofluidic implementations include a small sample volume (2.5 microL), reduced energy consumption and compatibility with other microfluidic blocks. These features make this device an attractive option for "lab-on-a-chip" and portable applications.