Directional solidification experiments have been carried out on different Pb-Sn alloys as a function of temperature gradient G, growth rate V and cooling rate GV. The specimens were solidified under steady state condition with a constant temperature gradient (50 degrees C/cm) at a wide range of growth rates ((10-400) x 10(-4) cm/s) and with a constant growth rate (17 x 10(-4) cm/s) at a wide range of temperature gradient (10-55 degrees C/cm). The primary dendrite arm spacing, lambda(1), and secondary dendrite arm spacing, lambda(2), were evaluated. This structure parameters were expressed as functions of G, V and GV by using the linear regression analysis. The results were in good agreement with the previous works.