Lint yield of cotton may be limited by N or B on sandy soils. It is possible that foliar applications of N and B could alleviate mid-season deficiencies and improve cotton (Gossypium hirsutum L.) performance on sandy soils. The objectives of this study were (i) to determine the response of cotton to foliar applications of N and B and (ii) to compare two sources of N applied to foliage of cotton. A field study with a factorial arrangement of three N treatments (no N or one of two N sources at a seasonal foliar total of 16.6 kg N ha^-1) and two B treatments (no B or a seasonal total of 0.33 kg B ha^-1) was conducted for two years on a Beulah fine sandy loam. The foliar applications were made at early bloom, mid-bloom, and late bloom. The six foliar treatments were a check solution of water, B (as H(3)BO₃), triazone-N (24% of N as S-tetrahydrotriazone, C(3)N(3)H(7)O), triazone-N plus B, urea-N, or urea-N plus B. Leaf blade mineral composition was determined after the second foliar spraying. Leaf area index (LAI) and CO₂-exchange rate (CER) of the fourth uppermost leaf were determined after the third spraying. At maturity, boll retention (total bolls/total flowers), lint yield, and fiber properties were determined. Averaged across years, lint yields were significantly higher in the check, both urea treatments, and the triazone plus B treatment than in the B only treatment. The lint yield of the triazone-N without B treatment was not significantly different than any other treatment. The lower lint yield of the B only treatment in this study led to a significant N x B interaction. However, foliar B applications do not normally reduce lint yields. Foliar applications of either triazone-N or urea-N increased leaf blade N concentration but did not affect leaf blade B concentration. Foliar applications of B increased leaf blade B concentration but did not affect leaf blade N concentration. There were no N x B interactions on leaf blade N or B. Lint yield was negatively correlated to leaf blade sodium concentration. Foliar applications of N or B did not affect boll retention, LAI, or CER and had little effect on fiber properties. The variables obtained from the triazone-N treatment were not significantly different than those from the urea-N treatment. The results of this study suggest that the increases in leaf blade N and B concentration obtained from foliar fertilization in cotton do not necessarily change cotton's physiological or agronomic characteristics.