Length at maturity computed for female flathead catfish (Pylodietus olivaris) from marshes of southwest Louisiana was 589 mm. Empirical data showed males approach maturity in the 390-439 mm size range. The length-weight regression for flathead catfish was best described by: Log W = -8.9640 + 3.3732 Log L, where W = weight in kg and L = length in mm, r = 0.97. The computed total length-collarbone length conversion equation for flathead catfish was Y = 10.3428 + 0.7251, where Y = total collarbone length in mm and X = total body length in mm, r = 0.99. Dressout-live weight relationship for flathead catfish was Y = 0.3308 + 0.7123 X, where Y = cleaned ( headed and eviscerated) weight in kg and X = live weight in kg, r = 0.70. Computed length at maturity for blue catfish (letalurus fureatus) was 481 mm.