The Pb-Sn codeposits were prepared by electrochemical deposition. SEM, XRD, and EPMA were applied to study morphologies and microstructure of the deposits. With the proportion of two kinds of cations in electrolyte solution varies, the deposits exhibit abundant morphologies and abnormal nonequilibrium microstructure. The Pb0.9Sn0.1 dendritic deposit consists of the center part with Pb-based solid solution and outer part with pseudo-eutectic, whereas the tip of the side-branch is covered with Pb-based solid solution. The Pb-Sn deposit with rich Sn consists of branches, subbranches, and globules forming on the tip of each subbranch. The texture of the globule transits from pseudo-eutectic to Pb-based solid solution with the growth of the globule. The formation mechanisms are discussed based on the electrochemical reaction dynamics. (C) 2004 Elsevier B.V. All rights reserved.