Lymphocystis is a viral disease of fish primarily in marine and brackishwaters. Here we report the cloning, expression, and the serological applications of the lymphocystis disease virus (LCDV) major capsid protein (MCP). The MCP gene was amplified by PCR from the genomic DNA of LCDV isolated from Schlegel''s black rockfish, Sebastes schlegeli, and expressed in E. coli. Mouse antisera raised against the purified recombinant MCP (rMCP) reacted with the viral MCP in an immunofluorescence assay, indicating that this rMCP would be useful for serological studies of field samples.