The development of small molecular mass Hsp90 inhibitors has become an increasingly competitive field of research in recent years. Progress in preclinical and clinical research has provided increasing evidence that Hsp90 represents a promising molecular target for the treatment of cancer and other diseases. Although many challenges remain, recent clinical trial results for the most clinically advanced inhibitors indicate that clinical proof of concept in oncology therapy is achievable, and that Hsp90 inhibitors have the potential to contribute to the collection of anticancer treatments available to clinicians and patients in the near future.