This fourth edition of Common Diseases comes just over 10 years after the first. There has been change and counterchange in the primary health care (PHC) field. One change has been the tendency to replace 'general practice' by 'PHC'. Vocational training has become compulsory. With larger group practices have come formalized teams and teamwork, increasing con­ cern with the business side of general practice and attempts to achieve best values for money and maximal profits. On the clinical side there have been enthusiasms for prevention, early diagnosis, anticipatory care, screening and quality initiatives. As a counterchange it is necessary to remind ourselves that the real essence of general practice, PHC, or whatever title we give it, is 'personal doctoring' of people as individuals in family units. All the changes mentioned will achieve less than expected without good continuing doctor/ patient personal care. But even this is not enough. Good general practice demands a sound knowledge of the nature of disease in the community. Not only are traditional diagnostic and therapeutic skills necessary, but also application of an understanding of the frequency and distribution of the diseases and an awareness of their likely natural history - their course and outcome.