Bismuth (Bi)-Cadmium (Cd) eutectic alloy was melted in a graphite crucible under vacuum atmosphere. This alloy was directionally solidified upward with a constant growth rate, V (8.33 mu m/s), and different temperature gradient ranges, G (1.93-4.74 K/mm), and also with a constant G (4.74 K/mm), and different V (8.33-167.32 mu m/s) in the Bridgman type directional solidification furnace. The lamellar spacings lambda (lambda(a), lambda(a)*, lambda(m)*, lambda(M)*), were measured from both transverse section (lambda(a)) and longitudinal section (lambda(a)*, lambda(m)* lambda(M)*), of the specimens. The variations of lambda(i) with respect to G and V were determined by using linear regression analysis. The dependence of lamellar spacings lambda(i) on undercooling (Delta T) was also analysed. The variations of Delta T with G at constant V and with V at constant G were investigated. According to these results, it has been found that lambda(i) decreases with increasing values of G and V. Also Delta T increases with increasing V for a constant G and with increasing G for a given V, respectively lambda V-2, Delta T lambda, Delta TV-0.5 and lambda(2)G values were determined by using lambda(i), Delta T, V and G values. The results obtained in this work have been compared with the Jackson-Hunt eutectic theory and the similar experimental results (c) 2006 Published by Elsevier B.V.