A study of the effectiveness of individual anti-smoking advice was conducted on male smokers visiting a human dock. The intervention group (169 male smokers) were shown photographs depicting the health hazards of smoking with an explanation by tape recorder and headphone. Controls (187 male smokers) did not receive this instruction. In the intervention group, immediately after the instruction, and in the control group, approximately 60% expressed a desire to stop or decrease their smoking. Six months later there was no significant difference in the two groups in the proportion that stated that they were not smoking (8.9% in the intervention group and 5.9% in the control group). Some subgroups in the intervention group, such as those whose smoking index was less than 400 and those who had attempted to quit smoking in the past, had significantly higher quit rates than corresponding subgroups in the controls. Smokers who restricted their smoking in certain locations such as public areas had high quit rates in both groups. Standardized quit rates were utilized, adjusted for current age, age of smoking initiation, smoking index and past experience in smoking cessation. Immediately after receiving the education, the proportion that regarded smoking as a risk factor in gastric cancer, gastric ulcer, chronic bronchitis and as having a harmful effect on the fetus, was significantly larger in the intervention group (about 50-70%) than in the controls (about 30-60%). More than 90% of each group regarded it as a risk factor in lung cancer, and about 60% in myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)