During the last 3 decades, the mortality rates of amyotrophic lateral sclerosis (ALS) markedly increased in various countries, including Italy. This finding has been attributed to factors such as better case ascertainment or changes in the demographic structure of the population, or to unknown environmental factors. The longitudinal Gompertzian analysis represents an alternative way to evaluate this phenomenon. Mortality from ALS in Italy in the last three decades fits in well with the Gompertz model in both sexes, and also with specific mortality of different birth cohorts. The 'environmental' factor R0 showed a decreasing trend in the most recent birth cohorts. Therefore, according to this model, the increase in ALS mortality during the last few decades may be due to the increased strength in competing for mortality of ALS compared to other diseases.