Recent surveys show that morphine treatment of female rats may have long-term effects on their offspring. The purpose of this study was to analyze potential effects of pre-mating morphine-chloride exposure on the pain sensitivity in the offspring. Wistar dams weighing 200–250 g were treated with morphine doses from 10 to 60 mg/kg at 12 hours intervals during 7 days before mating with drug-naive males. On postnatal day 30 pups were tested for pain thresholds in the "hot plate" test. Pups received 10 mg/kg of morphine, i.p., daily at postnatal days 41–47 to evaluate the changes in the nociception. Tail-flick latencies were measured twice at postnatal day 41 and postnatal day 47. Measuring the pup's weights during the first weeks of postnatal development revealed that offspring from morphine treated mothers (M-group) had significant weight loss at age of 20–30 days (p<0.05). We did not find any changes in paw-lick latencies in the "hot plate" test. Analysis of the baseline pain thresholds in the "tail flick" test (41 day) revealed hypoalgesia (increase in tail flick latencies) in M-pups compared to control (p<0.05). M-group showed lower baseline latencies on day 47 compared to day 41 (p<0.05). Furthermore, we found a reduction in the development of tolerance to acute antinociceptive effect of morphine compared to the control pups. Our data reveals that "hot plate" and "tail flick" tests have different mechanisms of pain conducting. These results indicate that pre-mating chronic morphine exposure can have long-term effects on pain thresholds and nociception of the offspring.