Correction to “Modeling the functional effects of allosteric modulators at pharmacological receptors: An extension of the two-state model of receptor activation”  In the above article [Hall D (2000) *Mol Pharmacol* **58:**1412–1423], typographical errors were made in several equations. We apologize for any confusion or inconvenience caused by these errors.  The inequality on page 1419 should appear as(δ>(1+αL+γM[B])/αγ(1+L+M[B])) Equation 3 (page 1421) should be[A]Bound[R]T=[A]1+L+M[B](1+βL)K(1+αL+γM[B](1+αβδL))+[A] The first equation in the second column of page 1421 should be12K[A](1+αL)1+L+K[A](1+αL)+γK[A](1+αβδL)1+βL+γK[A](1+αβδL)=[A]1+L+M[B]50(1+βL)K(1+αL+γM[B]50(1+αβδL))+[A] * The American Society for Pharmacology and Experimental Therapeutics