The concentration of nutrients in cotton petioles are affected by a number of different factors. An understanding of the affects of these factors is critical in an accurate interpretation of petiole nutrient analysis. The most common nutrients analyzed for in the semi-arid and arid west are nitrate-nitrogen (NO₃-N), phosphate-phosphorus (PO₃-P), and potassium (K)(3). This paper will review work done in the San Joaquin Valley on the effects of number of days after planting, time of day, soil analysis level, fertilizer type and rate, and days after irrigation. The work was performed by a number of researchers, and the author would like to acknowledge the cooperation of Dr. Tom Kerby, U.C. Cooperative Extension Cotton Specialist, Dr. David Goldhamer, U.C. Cooperative Extension Area Irrigation Specialist, Ms. Stephanie Johnson, U.C. Cooperative Extension Farm Advisor, Tulare County, Mr. Kater Hake, U.C. Cooperative Extension Farm Advisor, Kern County, and Dr. Dick Bassett, U.C. Agronomist.