The author describes his experiences due to his inherited colour vision deficiency, as a child, as student and as a medical practitioner, when he had certain difficulties in clinical work. He quotes from the literature on the clinical skills of physicians with this deficiency and gives an account of his own research that involved meeting and testing other doctors of medicine. This revealed a wide range of difficulties experienced by colour vision defective doctors in their practice of medicine with a potentiality for errors. Although there is a number of publications on this subject, the profession has made little response to them. This suggests that it is facing a dilemma that is inhibiting appropriate action. It is suggested that colour vision scientists and medical practitioners need more understanding of each other's discipline if progress is to be made. The advantages of screening of medical students and advising those found to have a deficiency are discussed and lines of research are proposed.