The effect of intraperitoneally administered nucleic acid components (nucleoside-nucleotide mixture) on the recovery from methicillin-resistant Staphylococcus aureus (MRSA) strain 8985N infection was studied in mice. Two experiments were conducted in which BALB/c mice were fed a nucleotide-free 20% casein diet for 30 days. On the 10th day, the mice were inoculated intravenously with viable MRSA organisms. The mice were intraperitoneally administered nucleoside-nucleotide mixture or saline (control) daily from the onset of the experiment (experiment 1) or from the day of inoculation (experiment 2). The survival rate in the nucleoside-nucleotide group in experiment 1 (70%) was significantly higher than that in the saline group (20%) (p < 0.05). In experiment 2, the survival rate in the nucleoside-nucleotide group (55%) tended to be higher than that in the saline group (36%) without statistically significant difference; furthermore, in the surviving mice, the viable MRSA organisms recovered from the spleen and the kidney were fewer in the former group than in the latter group (p < 0.05). The studies showed that the intraperitoneal administration either before or after the MRSA challenge of the nucleoside-nucleotide mixture was effective for the recovery of the mice from the infection.