A new fluorescence reaction for the detection of boric acid with resacetophenone and phosphoric acid has been described. None of the metallic radicles examined interferes while among the acid radicles chromate, bromate, chlorate, nitrite and fluoride do so to a limited extent. The reaction compares favourably with those described in the literature both as regards limit of identification and also interference. It has been shown that the test is applicable for the detection of micro-quantities of boric acid.