INTRODUCTION: Shortly after their introduction, fluoroquinolones were associated with reports of tendinitis and tendon rupture. During the past years, the number of reports has risen, possibly because of an increased use of fluoroquinolones. In thistudy, we describe the use of fluoroquinolones in the Dutch community and the possible public health effects of an association between fluoroquinolone use and tendon ruptures. METHODS: In the PHARMO drug database we identified all prescriptions for fluoroquinolones in the period 1991-1996. The incidence of fluoroquinolone use was expressed as the number of fluoroquinolone episodes per 1000 inhabitants in one year, and extrapolated to the Dutch population after standardisation on age and gender. The annual incidence of non-traumatic tendon ruptures in the period 1991-1996 was calculated with data from the nation-wide hospital registry. The expected number of fluoroquinolone attributable tendon ruptures was calculated on the basis of the use of fluoroquinolones, the number of non-traumatic tendon ruptures and an assumed relative risk of 1.5-10. RESULTS: In 1996, approximately 251,000 patients experienced 318,000 episodes of fluoroquinolone use in the Netherlands. Females used more often fluoroquinolones than males, and the number of episodes increased exponentially with age. In the period 1991 through 1996, the absolute number of fluoroquinolone episodes increased by 160%, from 122,000 to 318,000. The absolute number of hospitalised tendon ruptures increased with 28%, from 768 in 1991 to 984 in 1996. Assuming a relative risk of 1.5 to 10.0, 1 to 15 tendon ruptures could be attributed to fluoroquinolone use in 1996. Only 7% of the observed increase could be attributed to the increased use of fluoroquinolones. If the total increase of hospitalised non-traumatic tendon ruptures would be attributable to the increase in fluoroquinolone use, this would mean that the risk of non traumatic tendon ruptures to fluoroquinolones would be more than 250 times therisk during non-use. CONCLUSION: In the Netherlands, a large simultaneous increase in non- traumatic tendon ruptures and fluoroquinolone use was observed in the period between 1991 to 1996. Assuming a relative risk of 1.5 to 10.0 for tendon ruptures during fluoroquinolone use, only 0.5 to 7% of the increase in non-traumatic tendon ruptures could be attributed to the increased fluoroquinolone use. The increase in the incidence of non- traumatic hospitalised tendon ruptures in the Netherlands is not likely to be explained solely by the increased use of fluoroquinolones.