We studied surface organization of lipophilic guanosine derivatives with one, two and three alkanoyl tails in thin films on water surface and in Langmuir-Blodgett (LB) films transferred onto freshly cleaved mica substrate. The derivative with one alkanoyl group exhibits irreversible pressure-area isotherms and ribbon-like LB film structures. The derivatives with two and three side groups show reversible isotherms with similar critical surface pressures, while their LB film structures are quite different. The derivative with two tails forms films with flat terraces of micrometer size, while the derivative with three tails exhibits irregular thread-shaped assemblies. These observations demonstrate that molecular assembly of LB films of guanosine derivatives can be effectively manipulated by altering the number of attached lipophilic groups. (C) 2009 Elsevier B.V. All rights reserved.