Data on 63 patients who had had motorcycle accidents and who were admitted to four general hospitals in the Chung Chung Nam Do area from July/1993 to August 1993 were analyzed. The tool used for this study was a structured questionnaire which consisted of ten items on self-esteem, 18 items on health locus of control and 37 items profiling health promotion lifestyle. Injury severity scores were calculated based on data from the patients' medical records. The collected data were analyzed using the SPSS, yielding descriptive statistics, t-test, ANOVA, Pearson's Product Moment Correlation. The findings of this study are as follows. 1) Of the 63 injured motorcyclists, 35(50.6%) were helmeted and 28(44.4%) were nonhelmeted, and the nonhelmeted motorcyclists were predominantly young and male. The demographic variables for the helmeted and nonhelmeted groups were beterogeneous for age and occupation. 2) The results of the comparison between the two groups showed a statistically significant difference in the injury severity score(t=-4.70, p=0.000). The helmeted group had lower scores on injury severity score (9.00 +/- .93) than the nonhelmeted group(14.32 +/- 5.05). More than 60% of the nonhelmeted motorcyclists had brain injuries compared to only a third of the helmeted cyclists. 3) There was a statistically significant difference between the two groups on self esteem(t=4.5, 000). The helmeted group had a higher mean score (31.27 +/- 2.72) than the nonhelmeted group(27.46 +/- 3.80). 4) The means for Internal health locus of control (IHLC), Powerful others health locus of control (PHLC), and Chance health locus of control (CHLC) in the two groups were similar to instrument norms reported in other literature. The mean scores on the IHLC in the two groups were higher than scores on the PHLC or the CHLC. However, there was a significant difference between the mean scores for the two groups on the PHLC (t=2.85, p=0.006). 5) The mean score for the helmeted group on the health promotion lifestyle profile was higher than the mean score for the nonhelmeted group(107.30 +/- 11.10, 96.57 +/- 15.54 respectively), and there was a significant difference between the mean scores (t=3.64, p=0.001). The highest score for helmeted group on the health promotion lifestyle profile was in the health care domain. However, for the nonhelmeted group the highest score was in the exercise domain and the lowest score was in the health care domain. 6) With regard to the relationship between health promotion lifestyle, health locus of control and self esteem in the two groups, the correlation coefficient between health promotion lifestyle and internal health iocus of control for the helmeted group was 50(p<0.01). For the nonhelmeted group, there was no correlation between health promotion lifestyle and internal health locus of control. However, there were significant correlation between health promotion lifestyle and external locus of control (r=0. 46, p<0.01), and self esteem(r=0.495, p<0.01). 7) Among the demographic variables, age and education had an impact on individual's self-esteem. The modifying factors of age made a contribution to explaining health-promoting lifestyle. In the present study, more than 40% of the motorcyclists were riding without a helmet. The incidence of brain injury for patients riding without a helmet was nearly twice as high in the nonhelmeted rider as compared to the helmeted rider. The nonhelmeted motorcyclists in this study had lower self-esteem, obtained a higher score on the IHLC, and were not strongly engaged in performing health promotion activities as compared to the helmeted riders. However, some of the nonhelmeted riders who had a strong belief in PHLC were positively associated with engaging in health promotion activities. Based on the results obtained from this study, strategies to promote helmet usage for motorcyclists have to be developed.