Anterior crowding/ spacing are one of the major problems that inspire patients to undergo orthodontic treatment. Several factors associated with anterior crowding/ spacing includes arch width and length, mesio-distal tooth diameter and proportions. The aim of the present study was to evaluate the relationship of maxillary and mandibular base lengths to the amount of anterior dental crowding/ spacing in patients with complete class II malocclusions. A retrospective study was done with 152 patients who were divided into four groups according to the severity of pre-treatment dental crowding/spacing present in the mandibular arch. Measurements were performed on the pre-treatment dental casts and lateral cephalograms. Statistical analysis was done using t-test and chi-square test. Subjects with complete class II malocclusion and moderate to severe mandibular crowding [?3mm] have significantly smaller base lengths as compared to the subjects with slight crowding or spacing [<3mm]. There exists an inverse correlation between maxillary and mandibular base lengths and the severity of dental crowding and direct correlation with spacing.