A computer system DIROM for oligonucleotide-directed mutagenesis and artificial gene design has been designed for better experimental planning and control. DIROM permits searching for optimal oligonucleotides with respect to certain important parameters, namely sufficient energy of oligonucleotide-target hybridization, the secondary structure of oligonuc-tide and target DNA, the presence of alternate binding sites in the target DNA and terminal G/C pairs. It can also be used to plan polymerase chain reaction experiments, for optimal primer selection, in sequencing, etc. DIROM enables one to search for both existing and potential restriction sites, to perform vector + target sequence construction. The system consists of a set of original algorithms that formalize the empirical knowledge of oligonucleotide action as primers.