The concept of phage therapy to treat bacterial infections was born with the discovery of bacteriophage almost a century ago. After a chequered history its current renaissance is fuelled by the dangerous appearance of antibiotic-resistant bacteria on a global scale. As a mark of this renewed interest, the unanswered problems of phage therapy are now being addressed, especially for human use. Phage therapy in agricultural, food processing and fish farming industries is already successful and this review, whilst being aware of the potential drawbacks, emphasizes the need for further carefully controlled empirical data on its efficacy and safety in treating human and animal disease, especially in view of its numerous advantages over antibiotics. Finally the potential of phage therapy against bioterrorism and the emergence of second generation phage antibacterials based on phage-derived single-protein lysis systems are addressed.