A fair evaluation of the net benefits provided by pesticides is essential to feed the current debate on the benefits and consequences of the use of these chemicals. Pesticides provide many benefits, by killing agricultural and human pests. However, they also entail several types of costs, including internal costs due to the purchase and application of pesticides and various other costs due to the impact of treatments on human health and the environment. Here, we provide a comprehensive review of these costs and their evaluation. We define four categories of costs — regulatory costs, human health costs, environmental costs and defensive expenditures — that are either internal to the market, but hidden to the users, or external to the market and most often paid by a third party. The economic costs of pesticide use have been seldom considered in the literature and have undoubtedly been strongly underestimated in the past. Despite this underestimation, we found that overall hidden and external costs ranged from US$5.4 million (2013) in Niger in 1996 to US$13.6 billion (2013) in the United States in 1992. We perform an updated and more complete retrospective evaluation of these costs in the United States and show that they probably reached the value of US$39.5 billion (2013) per year at the end of the 1980s/start of the 1990s. We also re-evaluate past benefit- cost ratio of pesticide use in various countries and reveal that the cost of pesticide use might have outreached its benefits, e.g. in the United States at the start of the 1990s. We finally advocate that the key impact to be evaluated is the cost of illnesses and deaths triggered and/or favored by chronic exposure to pesticides. The benefit-cost ratio of pesticide use may have easily fallen below 1 if this cost had been taken into account. The quantification of this key cost is therefore urgently required for a more accurate evaluation of pesticide use and for regulatory purposes.