Short-fiber motes in cotton (Gossypium hirsutum L.), which have fibers shorter than one-half the length of the fibers on normal seeds, are either unfertilized ovules or underdeveloped seeds in which embryo growth ceased shortly after fertilization. Increased numbers of short-fiber motes reduce yield. In long-fiber cotton motes (fiber lengths longer than one-half the length of fibers on normal seeds), termination of embryo growth occurs some time after fertilization. Increased numbers of long-fiber motes reduce yield and fiber quality because less secondary wall is deposited on mote fibers. The objective of this study, conducted in Corpus Christi, TX, was to: (i) determine the frequency of mote production under rainfed and irrigated conditions, (ii) rank seed positions in locules according to probability of growth termination, and (iii) examine possible relationships between seed weight and mote production. Irrigation increased yield. Short-fiber mote percentages were the same in rainfed and irrigated cotton in 1993, but not in 1994 and 1995. In low-yield years, long-fiber mote percentages in rainfed cotton increased as the season progressed. When differences in mote frequencies among seed positions occurred, higher mote frequencies were associated with seed positions near either the locule apex or the pedicel. Some seed locations may be more sensitive to environmental perturbations than others. High frequencies of long-fibered motes were associated with locules in which the average seed weight was 60 to 110 mg (the lowest seed weight category).