A series of platinum dinuclear complexes with l-alkyluracil, cis-[Ph2(PtU)2(NH3)4] (NO3)2, cis-[Pt2(n-BuU)2(NH3)4](NO3)2, cis-[Ph2(BzlU)2(NH3)4](NO3)2 and cis-[Pt2(NaphCH2U)2(NH3)4](NO3)2 (head-to-head, where U=uracil), and with imide ligands, cis-[Ph2(SI2(NH3)4](NO3)2 (head-to-head), cis-[Pt2(DMGI)2(NH3)4](NO3)2 (head-to-head), cis-[Pt2(DMGI)2(NH3)4](NO3)2 (head-to-tail) and cis-[Pt2(DMGI)2(NH3)4] (NO3)2 (head-to-head, where SI = succinimidate, EMGI = 3-ethyl-3-methylglutarimidate and DMGi=3,3.dimethylglutarimidate) was synthesized, as well as platinum mononuelear complexes, cis-[PtCl(SI)(NH3)2] and cis- [Pt(SI)2(NH3)2]. The isomers of the dinuclear complexes (head-to-head and head-to-tail forms) were obtained separately by fractional recystallizations. Crystal structures of cis-[Pt2(SI)2(NH3)4](NO3)2 (head-to-head), cis-[Pt2(DMGI)2(NH3)4](NO3)2 (head-to-head) and cis-[Pt2(EMGI)2(NH3)4](NO3)2 (head-to-head) were determined by X-ray diffraction analysis. Cytotoxic activity was evaluated by the IC50 value using mouse sarcoma S-180 cells. Most head-to-head complexes are considerably active, while the corresponding head-to-tail analogues are inactive. The active complexes, in general, release ligands in saline at 37°C, and a relationship between hydrophobicity of the complexes and the IC50 value has been shown.