The purpose of the study was to find out the effects of intensive and extensive interval training on speed performance of athletes. To achieve this purpose of the study, forty five men athletes in the Department of Physical Education and Sports Sciences, Annamalai University, Annamalai Nagar, Tamil Nadu, India were selected as subjects at random. The selected subjects were divided into three equal groups of fifteen subjects each, such as intensive interval training, extensive interval training group and control group. The group I underwent intensive interval training programme, Group-II underwent to extensive interval training for three days per week for twelve weeks. And Group III acted as control group who did not participate any special training programmes apart from their regular physical education activities as per their curriculum. The following variable namely Speed Performance was selected as criterion variable and it was measured by using fifty meters dash. All the subjects of three groups were tested on selected criterion variable at prior to and immediately after the training programme. The analysis of covariance was used to analyse the significant difference, if any between the groups. The level of significance to test the ‘F’ ratio obtained by the analysis of covariance was tested at .05 level of confidence, which was considered as an appropriate. The results of the study revealed that there was a significant difference between intensive interval and extensive interval training group and control group on speed performance. And also it was found that there was a significant improvement on speed performance due to intensive and extensive interval training.