Recent studies have demonstrated the feasibility of using DNA-based ex
periments to compute solutions to combinatorial problems. However, a p
rerequisite for designing a computer useful in a wide range of applica
tions is the ability to perform mathematical calculations. The develop
ment of a DNA-based algorithm for addition is presented. The DNA repre
sentation of two nonnegative binary numbers is presented in a form per
mitting a chain of primer extension reactions to carry out the additio
n operation. To demonstrate the feasibility of this algorithm, a simpl
e example was executed biochemically.