Over the past few decades, there has been an increase in the number of multi-author papers within scientific journals. This increase, in combination with the pressure to publish within academia, has precipitated various unethical authorship practices within biomedical research. These include dilution of authorship responsibility, 'guest', 'pressured' and 'ghost' authorship, and obfuscation of authorship credit within by-lines. Other authorship irregularities include divided and duplicate publication. This article discusses these problems and why the International Committee of Medical Journal Editors guidelines are failing to control them.