Natural disasters can be classified into four main types: floods, earthquakes, cyclones and droughts. This paper compares these types of natural disaster in terms of four characteristics: predictability, scope, onset delay and lethality. Special attention is paid to the last of these characteristics. It is found that the mortality and morbidity associated with natural disasters has changed over time and varies between regions. The variation between regions correlates with differences in socio-economic conditions, the impact of a disaster in a poor area being much greater than the impact of a disaster of similar physical characteristics in a richer area; it appears that the impact of a disaster is as much a function of the local conditions as it is of the nature of the disaster itself. The paper then goes on to consider the nature of the emergency aid that is offered following emergencies. It concludes that it is often wasteful and inappropriate, coming too late into a situation in which conditions have already dictated that mortality and morbidity will be high. Suggestions are made of ways in which funds allocated to disaster relief could be better focused so as to reduce population vulnerability in the face of natural disasters.