Phenolphthalein was the best single test of the four investigated with the highest sensitivity of 1:10,000 with stained filter paper and cotton cloth together with its failure to react with plant peroxidases. Of the four tests, phenolphthalein together with leucomalachite were the most specific, leucomalachite was the least sensitive, and orthotolidine was the most sensitive. Tetramethylbenzidine and the orthotolidine tests were apt to produce interference color reactions with plant peroxidases. A maximum of 10 seconds for color development is required for reliable sensitivity, whereas in high blood concentrations, the color change will occur within 1 to 5 seconds. The various differences in the sensitivities reported by different researchers of presumptive tests for blood are the results of differences in the reagent concentrations, in the methods of sample preparation, expression of the results, and in the type of material containing the blood. On the basis of this study, phenolphthalein is recommended as the best single test for evaluating suspected bloodstains. 2 tables and 5 references (Author abstract modified)