To address the need for a high throughput, non-destructive technique for measuring individual cell mechanical properties, we have developed optical alignment compression (OAC) cytometry. OAC combines hydrodynamic drag in an extensional flow microfluidic device with optical forces created with an inexpensive diode laser to induce measurable deformations between compressed cells. In this, a low-intensity linear optical trap aligns incoming cells with the flow stagnation point allowing hydrodynamic drag to induce deformation during cell-cell interaction. With this novel approach, we measure cell mechanical properties with a throughput that improves significantly on current non-destructive individual cell testing methods.