We report here a system for automation of the dideoxynucleotide DNA sequencing method. The system consists of a Beckman Biomek 1000 robotic workstation which has been modified by the addition of a thin heater/cooler block directly on the instrument table. The heater/cooler block, which is regulated by a user-specified program integrated into the Biomek software, facilitates the use of both single- and double-stranded DNA sequencing procedures. Using this system, we are able to perform 24 sets of dideoxynucleotide DNA sequencing reactions in approximately 45 min. The reactions are performed in 96-well microtiter plates, using a prepared reagent pack which includes primer, enzyme, nucleotide mixes and radioactive label. Using standard gel electrophoresis technology, we are able to resolve over 500 nucleotides per sequencing reaction in about 5 h. Currently, we are able to perform three runs of 24 samples each, with subsequent gel analysis per 8-h period. Excluding autoradiography, this represents a daily data output of 36,000 base pairs.