Two methods for increasing the length of DNA sequence data that can be read off a polyacrylamide gel are described. We have developed a rapid way to pour a buffer concentration gradient gel that, by altering the vertical band separation on an autoradiograph, allows more sequence to be obtained from a gel. We also show that the use of deoxyadenosine 5'-(alpha-[35S]thio)triphosphate as the label incorporated in dideoxynucleotide sequence reactions increases the sharpness of the bands on an autoradiograph and so increases the resolution achieved.