Cancer is the second leading cause of mortality in developed countries. Irrespective of its malignant degree, certain histological types and locations, there is a number of authors who hold the view that a delay in diagnosis can be one of the factors leading to a fatal outcome of the disease. In this study an assessment was made of diagnostic delay in three locations (breast, bladder, and larynx) in which the disease usually begins with evident alarm symptoms. The natural history of disease, from the first symptom to hospital admission and clinical diagnosis, was reconstructed by means of a questionnaire administered to patients from May, first, 1989, to April, 30th, 1990. It is concluded that patient's responsibility is great for the diagnostic delay of breast malignant tumors, whereas such a responsibility can be attributed to the Health Maintenance System for the other two types of cancer, bladder and larynx.