In this project we are building a mathematical model to track the movement of spermatozoa during the process of chemotaxis. Our model is built on an off-lattice spherical biased random walk in 3-dimensional space, an extension of previous conventional deterministic 2-dimensional models. The sperm's type of movement is decided based on a comparison of the current and previous chemoattractant concentration which can be used to see whether it is approaching the egg. From the statistical analysis of the simulation results, we find that chemotaxis is an effective mechanism to increase the number of sperm reaching the egg.