Protein self-assembly is critical for numerous biological processes. Yet, assembly is rarely targeted by therapeutic agents, in part because it is hard to identify molecules that interfere with protein-protein interactions. Here we describe a simple fluorescence-based screen for self-association and its application to the assembly of hepatitis B virus capsids. These data are analyzed to identify kinetic and thermodynamic effects — both of which are critical for the viral lifecycle and for understanding the mechanism of assembly effectors. Suggestions are made for modification of this protocol so that it can be applied to other self-assembling systems. With manual pipetting, setting up a plate takes about two hours, the initial reading takes one hour, and the endpoint reading the following day takes about 5 minutes.