Tendonitis and tendon rupture are rare but recognized complications of fluoroquinolone therapy. Most reports of this problem have appeared in the rheumatology and pharmacology literature, and this topic has received little attention in the radiologic literature. We report two cases of fluoroquinolone-induced tendinopathy and describe their magnetic resonance (MR) and sonographic findings. Although Achilles tendinopathy is generally the result of repetitive injury, it is useful to keep other causes in mind. MR or sonographic findings of Achilles tendinopathy in a patient without history of antecedent trauma should prompt the radiologist to consider fluoroquinolone treatment as a possible causative agent.