When estimating yield of cotton, the weight of seedcotton or lint per boll is variable and often unknown. A sampling study was conducted in the Rio Grande Valley of Texas to determine if sufficient correlation existed between seedcotton weight and either boll diameter, seed number, or number of locs such that these parameters could be helpful in predicting the average seedcotton weight per boll. Seedcotton weight per boll was significantly related to all three parameters although each parameter was able to account for only of the fraction of the variability in boll weights. The parameters measured were poor predictors of individual boll weight, but may be useful for making inferences as to average boll weight. Boll diameter was as good a predictor of seedcotton weight as any other parameter or combination of parameters. Seedcotton weight was related to boll diameter by the equation: weight(g) = -3.96 + 0.253diameter(mm) (r ² = 0.169).