Abstract: The present invention relates to methods for detecting the presence of ribonuclease enzymes, more specifically to methods that provide for a visual detection assay. The methods entail contacting a test sample suspected of containing ribonuclease activity with a substrate containing a ribonuclease-sensitive internucleotide linkage flanked directly or indirectly by a fluorescence reporter group and a dark quencher, such that if a ribonuclease activity is present in the sample, the ribonuclease-sensitive internucleotide linkage is cleaved and the fluorescence reporter group emits a visually detectable signal. The present invention further provides novel nucleic acid compositions used as substrates for such assays and encompasses kits for performing the methods of the invention.