It is reported that a cumulated percentage of the interval between the onset of symptoms and the first visit to a doctor (patient delay) and that between the first visit and diagnosis (doctor's delay) among pulmonary tuberculosis (TB) patients demonstrate a straight line on the log-normal probability paper. Factors influencing the straight line nature of these delays were analyzed. The samples consist of 454 patients who were diagnosed between 1986 and 1988, from the area served by the Kochi Chuo Health Center. They were divided into two groups; 125 patients detected due to the manifestation of additional symptoms related to TB while being treated for other diseases (group A), and 329 patients detected only after the onset of TB symptoms (group B). Results are as follows. 1) When considering all patients (group A+B), patient delay among cases found through positive examination of tubercle bacillus and the doctor's delay among cases whose bacillus examination was negative demonstrated a straight line. However patient delay among bacillus negative cases demonstrated a downward tendency and the doctor's delay among bacillus positive cases demonstrated a upward tendency on the log-normal probability paper. 2) In the B group, both the patient's and doctor's delay demonstrated virtually straight lines among both bacillus positive and negative cases. However, in the A group, a straight line among bacillus positive cases was demonstrated, while a downward tendency was revealed among the bacillus negative cases.(ABSTRACT TRUNCATED AT 250 WORDS)