A simultaneous curve-fitting procedure for obtaining a set of tree height–diameter curves that do not cross, for a plot measured on several occasions, is described. It involves restricting one parameter of a three-parameter equation to be the same for all measurement occasions, keeping another parameter fixed for each measurement occasion, and allowing the remaining parameter to vary for each measurement occasion. An example shows that the simultaneously fitted height–diameter curves do not cross over the observed range of diameters for the plot and give reasonably accurate height estimates for the measurement occasions with inadequate height samples.