Motivation: Performing sequence alignment operations from a different program than the original sequence alignment code, and/or through a network connection, is often required interactive alignment editors and large-scale biological data analysis are common examples where such a flexibility is important. Interoperability between the alignment engine and the client should be obtained regardless of the architectures and programming languages of the sewer and client. Results: Clustalnet, a Clustal alignment CORBA sewer is described, which was developed on the basis of Clustalw. This sewer brings the robustness of the algorithms and implementations of Clustal to a new level of reuse. A Clustalnet sewer object can be accessed from a program, transparently through the network. We present interfaces to perform the alignment operations and to control these operations via immutable contexts. The interfaces that select the contexts do not depend on the nature of the operation to be performed making the design modular. The IDL interfaces presented here are not specific to Clustal and can be implemented on top of different sequence alignment algorithm implementations.