Entomology Research Branch . The citrus red mite,1 known generally in Florida as the purple mite, has become a major pest of citrus, especially in the last ten years. Since 1913 the Subtropical Fruit Insects Laboratory at Orlando has conducted many experiments with insecticides and miticides for control of this pest, and also experiments designed to reveal the causes of infestation increases. Sampling methods have been devised to measure natural infestations and also the control obtained with the many treatments that were tested. Sampling for reliable experimental data is at best a timeconsuming and expensive work. Through the years several methods have been tried in a continuing effort to obtain more reliable data at less cost of time and labor, and to find a simple method that might be useful also to citrus growers in checking their own groves. Experiments involving comparisons of insecticides or miticides for control of red mites are conducted in a single grove of uniform trees to avoid variations between groves. A randomized-block design is used (Spencer and Osburn, 1948). Ten compact blocks of trees are outlined on a map of the grove, each block including a tree for each treatment. By this method all treatments are subjected equally to any variations that may exist between different parts of the grove. Our present method of estimating infestations has several advantages. We use a hand lens in the grove, and so avoid collection and transportation of samples to the laboratory and use of the microscope. We examine only top surfaces of the leaves, since that is where most of the red mite eggs and crawling stages are found. This is simpler than examining upper and lower leaf surfaces and fruits, and gives larger numbers and less variation for equal time spent. The hand lens we use is a linen tester with frame having an opening, or field, one inch square. The opening is placed diagonally over the midrib on the upper surface of the leaf, and records are made of the numbers of crawling mites and unhatched viable eggs in the square. This is done for 25 leaves equally