Odour can be very characteristic, but there is great variation in the ability to detect odour, and in the names given to odours. Odours of fungi are usually characterised by comparison to those of other things, such as vegetables; but sometimes specific odours can be recognised, such as that of phenol (a compound present in some species of Agaricus).

Crush a piece of the pileus to intensify the odour, which may also be stronger when the fruit-body is warmed (such as after being carried in a container in your pocket).

Human scent receptors are rapidly saturated, and odour can seem to disappear (the ability to smell the odour will come back after a while). Some odours are difficult to characterise, but the range of options provided here covers most odours that will be encountered among agarics. Some odours are pleasant when faint, but unpleasant when strong, and some of the categories grade into one another (choose more than one option if unsure).

Choose this state if: the odour is the rather penetrating and unpleasant smell of rubber or burnt hair. Odours that are described as of rubber resemble the acrid odour present when handling bicycle or car tyres, or the smell of new wellington boots. This odour is particularly present among species of Phaeocollybia, and also in some species of Lepiota. The odour of Phaeocollybia has also been described as resembling the pungent smell of Thai fish sauce.