Aim: The study aim was to provide baseline information against the contradictory evaluations done in the public health sector, by enlighten the risk evaluation or identification by means of controlling irrational use in the society. Method: A cross sectional survey using self administered questionnaire was conducted starting from February to March 2009 at outpatient pharmacy department of Penang Hospital and from April to September 2009 from twenty difference pharmacy stores across whole Pulau Pinang. Data analysis was made against the theoretical framework of the study by using Statistical Package of Social Sciences 13®. Result: Study respondents were 1139 with 99.0% response rate. Almost equal distribution was made between man (53.9%) and female (46.1%). Majority of them were Malay (46%) next to Chinese (35.8%). Age group between 18 – 30 years largely (36.7%) responds to negative behavior of incomplete course of antibiotics. Marital status (married) three times more likely to irrational use of antibiotics as to single. The only predictor for statement ‘the effectiveness of treatment is reduced if a full course of antibiotic is not completed’ was significantly associated with more respondents having chronic medical condition getting the correct response (65.2% vs 58.9%, p=0.025). It has been found that knowledge level has less likelihood towards the sources of antibiotics and people taking antibiotics from different retail pharmacy are 200 percent more likely to develop or adopt irrational use pattern as to out-patient pharmacy of Penang hospital (RR 3.34, 95% CI 1.95 – 4.60). Conclusion: It is concluded that respondents to retail pharmacy were at high risk and more likely to be indulge in irrational antibiotic use as to Out-patients of Penang hospital.