A method for loading bits over a set of subcarriers of a multiple-carrier communications system comprises the operation of associating with the subcarriers respective numbers of bits chosen from among a plurality of available constellations. The method envisages definition of a performance target for the system and execution of bit loading, guaranteeing the aforesaid target on a plurality of subcarriers. The performance target can be a target error rate, such as a bit-error rate (BER), or else be transferred into a constraint, such as, for example, a threshold, in a metric of log-likelihood ratios (LLRs). In this case, there is preferably envisaged application to the signals received within the multiple-carrier system a function that estimates a signal to noise ratio on each sub-carrier. The aforesaid metric of log-likelihood ratios (LLRs) is hence defined as a function of said signal to noise ratios.