We have developed a simple and inexpensive method that improves sensitivity of protein and antigen detection in standard PAGE procedures. Our technique uses a sample microloader device with a funnel-like structure, filled with a 4% stacking gel. When attach to the top of a polyacrylamide slab gel the proteins in a sample are concentrated by electrophoresis into a small volume as they emerge from the device's narrow outlet. Our microloader has several advantages over previous devices, including simple assembly, high versatility and absence of cross-contamination between lanes. Addition of this device to a slab gel results in a 5-fold increase in the sensitivity of antigen detection in a western blot. As a result less protein is required for loading and signal detection. Our protocol is a straightforward modification of a standard experimental technique, and is especially useful when only limited sample quantities are available.