A rapid and versatile method has been developed for the synthesis of oligonucleotides which contain an aliphatic amino group at their 5′ terminus. This amino group reacts specifically with a variety of electrophiles, thereby allowing other chemical species to be attached to the ohgonucleotide. This chemistry has been utilized to synthesize several fluorescent derivatives of an oligonucleotide primer used in DNA sequence analysis by the dideoxy (enzymatic) method. The modified primers are highly fluorescent and retain their ability to specifically prime DNA synthesis. The use of these fluorescent primers in DNA sequence analysis will enable DNA sequence analysis to be automated.