Crossbite is the discrepancy in buccolingual relationship between the upper and lower teeth involving skeletal or dental components. Cross bites can be anterior or Posterior and skeletal or dental and unilaterally present or bilaterally present. Posterior crossbites as and when identified should be corrected since they are known to cause growth impairment. This study was done to report the prevalence of posterior crossbites and gender association in class II malocclusions. This retrospective study was done on case records of the patients who had reported to the orthodontic department, saveetha dental college, in the past 8 months. 1016 class II malocclusion case records in the age range 12-40 yrs were selected for the study, presence of posterior crossbites was evaluated in them and the frequency of crossbites was tabulated and statistical analysis was done in SPSS.The study showed that the overall prevalence of posterior crossbite in class II malocclusions was 3.8 %. single tooth crossbites(73.7%) were more common than multiple teeth crossbite(26.3%). No gender association for posterior crossbites was noted. In conclusion the present study reports a prevalence of 3.8% for posterior crossbites in class II malocclusion and there was no significant gender association.