This study determined the importance of Ophiostomatales fungi in the biology of individual adult Ips sexdentatus Boern. in Scots pine. We investigated factors possibly involved in success of rearing without Ophiostomatales, such as the sterilization technique, the presence of antibiotics, and the absence of yeasts. After sterilization of pupae, 866 adult beetles were reared in the media; the proportion of Ophiostoma-free mature adults was 99.2% and total mortality was about 13%. The most preferred rearing method used sterilized pupae which moulted on moistened filter paper and were transferred individually to separate vials where maturation took place on a sterilized phloem medium.The weight and size of Ophiostoma-free mature adults from semi-artificial media and, after establishment in logs, their fecundity and length of their egg galleries, were compared with those of naturally contaminated mature beetles obtained from logs. With the exception of a higher weight observed for adults matured in semi-artificial media, no essential difference was observed between the two groups. Ophiostomatales do not appear to play an essential role in the maturation and fecundity of I. sexdentatus adults.