Contamination of maize with aflatoxins was detected in Tamaulipas in 1989 and the Mexican government organized a Supervising Programme to check the maize crop of Tamaulipas from 1989 to 1992. The monoclonal immunoaffinity column method quantified by fluorometry was chosen as the official one. After detecting, in 1989, the first lots of contaminated maize, in 1990 87% of the crop was quarantined and the Supervising Programme was implemented. Laboratories were constructed in each warehouse that received the maize; one chemical analysis for aflatoxins was performed for every 100 tons of maize received and there were around 60000 analyses in the whole Programme (1989–1993). A random sampling method was applied, taking 2 kg from each truck. In 1991, the contaminated maize was dyed and separated as feed. Decontaminating methods with aluminosilicates and with ammonia were tested, but the cost was high and these practices were abandoned. A Technological Package for the fanners was organized by different institutions: the Ministry of Health, the Ministry of Agriculture, Conasupo, and the government of the State of Tamaulipas. This specified sowing time, insecticides, fungicides, fertilizers, irrigation periods, maize cultivars, etc. and had successful results in the field, in 1992, when lower quantities of total aflatoxins in maize were detected. On the other hand, the aflatoxin combination of maize persisted in storage areas, especially in the last week of July and the first week of August. The aflatoxin maize problem will be solved only when both field and storage contaminations are controlled.