Weight-length data were compiled from 289 redear sunfishLepomis microlophuspopulations. We applied the regression-line-percentile (RLP) technique to weight-length data for 150 redear sunfish populations to develop a new 75th-percentile standard weight (Ws) equation. The proposed RLPWsequation, log10Ws= −4.968 + 3.119log10TL where Ws is the standard weight in grams and TL is the total length in millimeters, is valid for fish >70 mm TL. The English-unit equivalent, log10Wg = −3.263 + 3.119log10TL whereWsis the standard weight in pounds and TL is the total length in inches, is valid for fish >3 in TL. We used the remaining 139 independent populations to evaluate the current [log10Ws= −5.164 + 3.227(log10TL)] and RLPWsequations for any length-related biases. We confirmed that the currentWsequation is length-biased. That is, relative weight (Wr) values significantly decreased with increasing fish length for far more populations (N=45) than they increased (N=7). We tested the proposed RLPWsequation with the same 139 populations, and found no consistent length-related bias inWrvalues calculated with the proposed RLP Ws equation (N=38, 29). Thus, we recommend the use of the proposed RLPWsequation for redear sunfish.