A major part of the carbon and nutrients in terrestrial ecosystems is in the tree component and it is therefore imperative to have appropriate methods for estimating tree biomass. To reduce the need for destructive sampling, biomass can be estimated from an easily measured property such as stem diameter, at specified height, by using an allometric equation. A substantial number of allometric equations have been developed for various climatic zones, forest types and tree species, using a variety of algebraic forms and parameter values. Anybody who wishes to use such equation for a new situation is faced with a difficult choice among the various equations, the result of which may vary over a factor 2 at least when applied to a specific data set.