All scientific disciplines requires reasoning power and it is one of basic requirement in the study of mathematics and science programmes at all level of education viz. primary, secondary and higher education. Anything that an individual does involves reasoning which is directed towards solving life problem or achieving a goal. The study was planned to seek answers to these questions viz.1. Whether there exist difference in scientific interest among boys and girls, 2. Whether there exists difference in reasoning ability of boys and girls and 3. Whether there exist any significant correlation between scientific interest and reasoning ability. The results indicate that there is no significant difference in scientific interest as well as reasoning ability of girls and boys. The coefficient of correlation between the scientific interest and reasoning ability of the ninth graders was found to be 0.837 which was found significant at 0.01 level of significance in the study. The implication of the research is that interest forms the basis of reasoning power and hence developing scientific reasoning is one of challenges of classroom teaching in the modern scenario.