The present invention relates to a method of detecting a base at a pre-determined position in a nucleic acid molecule by performing enzymatic detection reactions using base-specific detection oligomers, where each oligomer is specific for a particular base at the predetermined position, and then comparing the enzymatic detection reactions to determine which base is present at the position, with an enzyme-disabling agent being present during the enzymatic detection reaction. In preferred embodiments the enzymatic detection reaction is an oligomer elongation extension reaction, catalysed by, among others, polymerase or ligase. Also disclosed are methods of performing the assay in a liquid phase and on microarrays.