The pilling behavior of polyester/viscose, polyester/viscose/Lycra(R), and %100 cotton fabrics, is investigated in both normal and wet conditions. The experimental results show that the pilling tendency of fabrics in the wet state is directly related to the constituent fiber tenacity in the wet state. We also test three different pilling testers, the Martindale wear & pilling, the ICI pilling box, and the pilling drum, using both gray and finished fabric samples to investigate the sensitivity of different testers to various fabric parameters. In the gray state, the pilling box is sensitive to changes in the fiber blend ratio, weave type, and fabric stretch direction (mono or bi-stretch). The pilling drum exhibits a similar tendency, except that it is not sensitive to weave type. However, Martindale test results indicate that this apparatus is sensitive only to the yam count and stretch direction of fabrics with spandex filaments, In the finished state, the picture changes dramatically, because the pilling box is sensitive to the yarn count, yam twist, and stretch direction of fabrics with Lycra. The pilling drum again exhibits a similar tendency, except for weave type. The martindale, on the other hand, is sensitive to the yam count, yam twist, and stretch direction of fabrics with Lycra. Generally, the Martindale gives worse pilling grades than the pilling box and pilling drum. Since the test results show that each tester has a different sensitivity for different factors, we recommend using at least two different testers to obtain reliable results, one of these being the Martindale while the other might be either the pilling box or drum.