Soil and tissue tests help determine the N status of soils and plants. Because of a lack of accurate soil or plant tests, there are no leaf or soil tests recommended by the Extension Service in Louisiana for determining the N status of cotton soils or plants. This project helps determine the leaf N concentrations of the uppermost, fully mature, leaf blade associated with N deficiency in cotton for Louisiana and Mid-South cotton. Nitrogen-rate fertilizer field experiments were conducted at 12 research station and farm sites in Louisiana, Arkansas, Mississippi, and Alabama in 1997. Data from some of the sites were used to determine the critical value for leaf-blade N. Preliminary results indicated the leaf-blade total N % associated with N deficiency in cotton were at concentrations less than the values listed below: at 1^st pin-head square 4.6% N; at early-bloom 4.0% N; at mid-bloom (defined as 3 weeks after early bloom) 3.8% N; and at cut-out 3.3% N. Critical values at pin-head square and cut-out are not accurate but demonstrate the drop in critical values as the season progresses. The accuracy was poor at mid-bloom because mid-bloom was near cut-out at some sites in ‘97. Critical values for the 1997 season were about 0.2% less N than those optimized from the 1996 data.