Field and growth room studies were conducted between 2001 and 2005 to study the effect of the plant growth regulator ChaperoneTM on cotton (Gossypium hirsutum L.) plant nitrogen levels, plant protein levels, and yield. In addition, the research was designed to test if increased levels of protein from Chaperone also increased endotoxin levels in transgenic cotton, and thereby subsequently improved bollworm mortality and yield. Preliminary studies revealed that the optimum rate and timing of Chaperone was 5 oz/acre applied once at the start of flowering. Upper expanded main-stem leaves were sampled 10 days after Chaperone application for protein and endotoxin determinations, and insect mortality. In field studies, Chaperone at 5 oz/acre applied at first flower compared to the untreated control increased yield by an average of 8%. One week after application, there was an increase in petiole nitrate levels by 12% and in proteins in squares by 13%. In addition, there was improved expression of the Bt endotoxin protein in the squares by 6%. The increased endotoxin protein resulted in an average 10% higher mortality of bollworms feeding on treated plants compared to untreated leaves 10 days after application. These results were confirmed in two growth room studies. A growth room study using three temperature regimes (30C, 33C, 36C, and 39C) showed that foliar-applied Chaperone under elevated temperatures above 33C maintained higher levels of proteins than the control plants, and therefore improved the efficiency of endotoxin expression. The improved protein levels from foliar applications of Chaperone, particularly under high temperatures, may improve the overall physiological functioning of the cotton plant. Data from the growth chamber and field studies showed that foliar applications of Chaperone may be a viable means for enhancing lint yields in cotton through the enhancement of plant protein levels. Furthermore, the enhanced protein status contributes to improved late-season endotoxin levels in the squares, which contributes to increased mortality of bollworms feeding on the treated plants.