Changes in cotton fiber quality and attachment forces between foreign-matter particles and fibers were studied at different stages from the time of harvest through lint cleaning to develop new and less damaging methods for removing foreign-matter particles from cotton fiber. The study involved 75 samples collected from five field locations near College Station, Texas, including three replications and five harvesting and processing treatments: (1) hand picked and hand ginned, (2) machine picked and hand ginned, (3) machine picked, seed-cotton cleaned, and hand ginned, (4) machine picked, seed-cotton cleaned, and machine ginned, and (5) machine picked, seed-cotton cleaned, machine ginned, and one-stage lint-cleaned. A microscope was used to identify foreign-matter particles in each sample. Physical characteristics of the particles and their attachment to fibers were investigated and classified. Results indicated that each machine-fiber interaction during the harvesting through ginning process had the net effect of decreasing the size of foreign-matter particles. The particles had no obvious difference in shape across the processing stages. The tightness of particle-fiber attachment, the number of neps, and the short-fiber content differed significantly as a function of mechanical interactions: they increased as the number of mechanical interactions increased. Processing through the gin stand was a major contributor to the increase in short fiber content. The majority of the foreign-matter particles were leaves, but proportions of the particle categories changed with stages of processing. With an increased number of mechanical interactions the proportion of leaf particles decreased and the proportion of seed-coat fragments and stems increased.