A compact, laser desorption tandem time-of-flight mass spectrometer is described. The instrument incorporates two dual-stage reflectron analyzers and a collision region for producing product ions by collision-induced dissociation. Selection of ions of a particular mass is accomplished by deflection of ions from stable trajectory angles entering the second reflectron, while the use of a pulsed valve for introduction of the collision gas obviates the need for differential pumping of the collision region. Initial results are presented, as well as a discussion for optimizing the performance of tandem time-of-flight instruments.