Abstract: A user programmable deductive spreadsheet is implemented as an add-in to an existing mathematical spreadsheet program and allows the use of a logic programming language such as Prolog via a familiar spreadsheet interface. A syntax is provided whereby a set of multiple values can be stored in a cell and can be operated on recursively by an expression in another cell. Rows and columns can be given user defined names and cells can be referenced by row and column name. Cells can reference cells in other spreadsheets or can reference an entire spreadsheet in one cell. A cell expression can reference itself. Logical, arithmetic, and lifted operators are provided. Spreadsheets can be defined as a transformation of another spreadsheet. When no negative or aggregate operators are used in the cell expressions, the meaning of the spreadsheet is given in terms of least fixed points. Otherwise, the meaning is given in terms of perfect models.