The main purpose of this experiment was to study the effect of persuasive messages based on Kohlberg moral resoning theory on attitude change. In addition there were other independent variables, namely, familiarity with the persuasive messages, sex and rigidity. After the subjects had read the high moral reasoning messages or low moral reasoning messages or control messages, the attitudes and moral reasoning  ability of subjects were then assessed. 
                The sample consisted of 120  subjects of which 60  were males and 60 were females. They were secondary school students  at  Huathapanwittayakom school in 
Ubonratchathanee province. These students were third stage users of  moral 
reasoning. All subjects were assigned randomly to either one of the two experimental 
groups or  a control group. Each group of students consisted of 10  males and 10 females 
of highly rigid personality, 10  males and 10  females of low rigid personality with the total 
of 40 students. The first and the second experimental groups read high leveled and low  leveled moral reasoning messages. 
           Both of the high and low messages were on the same four issues, two of which 
were highly familiar topics ( issues on "teacher" and "snake" )  and two less familiar ones (issucs on "buying Thai goods" and "touring foreign countries") while the control group read controlled messages. Then the attitudes  tomards the 4 issuse were assessed by two different attitude tests. The Osgood' s method and the Likert's method were used to measure the affective compenent and the behavior intention compenent respectively. 
            There were five important findings. 
            First; the main effect of the persuasive messages was found on attitudes. The subjects whoread the high and low moral reasoning messages had significantly higher attitude scores 
on the 4 stories than the subjects who read the control message. When the attitude towards individual issue was examined it was found that the affective compenent of attitude towards 
" teacher" varied according to the levels of the messages received. In other words, the students who received high level message were more favorable towards "teacher" than the control 
subjects. These findings clearly supported the major hypothesis of this study. On the other hand, the behavior intention component of attitude towards teacher did not differ among the three groups of subjects. The results on 3 other issues were the same as that of allissues combined. 
            Secondly;  when attitude scores were analyzed according to the more and less familiar stories. The two types of contents yielded different results only when the affective component of attitude was analyzed. In more detail, the low leveled readers showed more  favorable  attitudes 
towards the issues than the control groups only when the less familiar issues were used, 
otherwise, the high and low message groups were equally favorable. 
         Thirdly;  when examined the main effect of sex, male and female students showed no difference on the two types of attitude. Furthermore there was no interaction between sex and persuasive messages. 
            When divided male and female students on comprehension  scores  of  persuasive 
messages in the low comprehension group, male students  showed significantly higher affective component of attitude than female students.  In the high-comperhension  group, female 
students showed significantly higher behavior intention towards buying Thai  goods than 
male students. 
            Fourthly;  There was no difference in both components of attitude of the high and low rigidity subjects. There was also no interaction between rigidity and levels of moral reasoning messages. 
          Finally;  The results showed that the group of students who had read the messages pertaining to different levels of moral reasoning, were not different in moral reasoning ability after reading the messages. 
          This experiment showed that the persuasive messages with high level of moral reasoning could greatty affect students' attitude change, especially or the story of "teacher". Among the students who highly comprehened the persuasive messages, the female 
students showed greater change in behavior intention than male students, especially on story of buying Thai goods. Thus there was a story implication that this type of persuasive technique could lead female students to change their behavior as well.