Haemophilia continues to be a prime target for a variety of gene and cell-based therapies. Pre-clinical successes in both mouse and dog models of the disease have been documented with a variety of approaches over the past decade, and there have now been six small clinical trials of gene transfer in haemophilia. To date, the only significant adverse events documented in these trials have been related to host immune responses, indicating that immunologic barriers continue to represent the major obstacle to achieving success of gene transfer in humans. Despite these challenges, new strategies are being explored with novel serotypes of viral vectors and with the use of transient periods of immunosuppression to attenuate the immune response to the vector and transgene product following gene delivery. Two new clinical trials, both using AAV vectors, will likely start within the next year, and additional large animal pre-clinical studies using other viral vector-mediated approaches for gene transfer are expected in the near future.