To test the hypothesis that testosterone stimulates masculine social behaviors by inducing transcription of messenger ribonucleic acid (mRNA), we studied the effects of cordycepin, an adenosine analog that preferentially impairs synthesis of polyadenylated mRNA. When infused into the medial preoptic area of castrated male gerbils an hour before they received systemic injections of testosterone propionate, cordycepin almost completely blocked recovery of sexual behavior but did not affect recovery of scent marking. In gerbils given saline infusions, both behaviors were restored. When treatments were reversed, sexual activity resumed in males previously exposed to cordycepin and declined in males now receiving the drug. Cordycepin also blocked reinstatement of sexual behavior by the two major metabolites of testosterone, estradiol and dihydrotestosterone. Thus it does not suppress sexual behavior simply by suppressing synthesis of aromatase or 5 alpha-reductase. Again, cordycepin had no effect on scent marking although this behavior is sensitive to other drugs that inhibit transcription or translation. The data suggest that testosterone may stimulate sexual behavior and scent marking, respectively, by inducing transcription of polyadenylated and nonadenylated mRNAs.