Silver nanocrystals with controlled particle size were prepared by reduction of silver nitrate with sodium borohydride in the presence of trisodium citrate and then silver nanorods were synthesized by using the nanocrystals as seeds. The aging has obvious influence on the small nanocrystals but little influence on the large nanocrystals, implying different structural defects on the crystal surfaces of the two kinds of nanocrystals. The use of silver nanocrystals prepared by addition of NaBH4 all at once and prepared at 0 degrees C helps produce the most silver nanorods with maximum aspect ratio. Only the smaller and slightly aged nanocrystals can be used as seeds for the formation of silver nanorods with high aspect ratio. The effects of concerned parameters of silver seeds can be applied to the synthesis of other anisotropic nanomaterials by a seed-mediated growth approach. (C) 2012 Elsevier B.V. All rights reserved.