In this lab exercise, students will work in cooperative teams to test the antimicrobial activity of an antiseptic or disinfectant using a modified use dilution assay as described by Benson (1). In the use dilution assay, paper clips are submerged in the antimicrobial agent, followed by a neutralization in sterile water and incubation in broth to determine the effectiveness of a particular agent. Vinyl paper clips are easier to manipulate than pins as recommended by Benson (1) and are preferable to metal substrates suggested by Johnson and Case (4) since metals can be inhibitory to the growth of most organisms (2). Students will use the scientific method to answer a question relating to the efficacy of a disinfectant or antiseptic. They will develop a hypothesis, design an experiment to test that hypothesis, and collect and analyze data. Efficacy of the disinfectant or antiseptic is determined by the inhibition of growth in broth tubes using optical density as a measure of growth. Following completion of the work, students will report their results to the class and a comparative analysis of the antimicrobic agents may be performed.