Dimensional change and profile development in the melt spinning process of polyethylene terephthalate hollow fibers were studied through the numerical simulations and experimental results. The simulation predicts the final dimensions and profiles development of the hollow fibers at various positions from the die. Experimental results show that the melt extruded from the spinneret coalesces initially to form a hollow inner core and the cross-sectional shape holds for over the whole spinline with only variation in the hollow portion. Analysis of the effect of spinning parameters on hollow portion shows that the spinning temperature, mass throughput rate, and take-up speed are the most critical variables in controlling the hollow portion followed by quench air velocity. The quench air temperature has relatively less effect than the other variables. As the mass throughput rate and quench air velocity increase and the take-up speed and spinning temperature decrease, the hollow portion increases. To investigate the effect of die geometry, die having a different ratio of inner to outer diameter was used. The effect of change of process variables decreases as the die gap becomes narrow.