The invention concerns a procedure for measuring the biodegradability of a sample, the sample being placed in a culture solution, the solution being aerated, the quantity of carbon dioxide liberated from the solution being determined, and the biodegradability being determined on the basis of the liberated carbon dioxide quantity. As taught by the invention, the carbon dioxide which has been formed is conducted into a non-precipitating alkali solution, the electrical conductivity of this solution is measured, and the quantity of carbon dioxide absorbed in the solution is determined on the basis of electrical conductivity.