Driving buses in London is an occupation in which the standards of fitness have been defined and in which the frequency of, and clinical reason for, exclusion from the occupation have been recorded. The criteria of fitness to drive a passenger vehicle are physical capability to handle controls (including good eyesight) and absence of conditions liable to cause sudden collapse or excessive fatigue with consequent liability to accidents. Some factors which may be overlooked as causes of collapse are idiopathic epilepsy which may first appear in middle life, carcinoma of the bronchus which commonly metastasizes in the brain and may cause fits, and laryngeal vertigo (cough syncope) which is much commoner in chronic bronchitis than is often realized. When medical standards to maintain public safety and the man9s own health were applied to applicants to drive London9s buses, 5·3% of the applicants were rejected on general medical grounds and a further 13·3% were rejected for sub-standard vision and colour vision. All the applicants had experience of driving heavy vehicles and were otherwise acceptable as drivers. Continued surveillance during working life, especially after sickness absence, of those involved in public safety is essential. During 1956, 23% of the examinations of bus drivers, who had been off sick for 28 days or more or for certain specified conditions, resulted in temporary or permanent exclusion from driving. This compares with 1·5% of examinations for licence renewal and 5·7% at age 65 and above. Cardiovascular disorders accounted for 26% of the causes of rejection during 1956, one-third of these being due to hypertension and one-half to coronary heart disease. No one who has had clinical coronary heart disease is allowed to drive London Transport buses because of the known increased chance of recurrence. Periodic examinations revealed a number of hypertensives but the majority of the “coronary cases” were revealed by sickness absence. Electrocardiography at periodic examinations does not, at the present, enable those who will have coronary heart disease to be recognized. Experience shows that the standards adopted are practicable and effective so far as bus drivers are concerned, and that careful assessment of fitness after sickness is as important as routine medical examination in maintaining public safety.