Neps, formed by tight and dense entanglements of fibers, are among the most disruptive structures found in cotton lint. There is general agreement that the vast majority of neps are formed due to the mechanical stresses, starting at harvest but primarily affected by ginning and by opening and cleaning operations in the textile mill. As such, neps are much more difficult to eliminate from the fiber than impurities such as dust and trash particles. This is because mechanical handling of cotton fiber usually results in new neps being created, even as existing neps are being removed. The primary objective of this research was to identify the factors affecting neps formation under the action of mechanical handling of cotton lint. Laboratory trials were conducted on custom-made openers in order to quantify neps generation independently from the cleaning effect. This paper is a progress report on results of these trials and on the main factors affecting nep generation potential.