Pyrethroid insecticides are very widely used in agriculture and household due to high effectiveness and low toxicity to humans. We have described a case of a fatal oral intoxication with decis, the insecticide containing pyrethroid (deltamethrin) in a hydrocarbon base. Pyrethroids, including deltamethrin, undergo rapid biotransformation by liver enzymes, which limit their systemic toxicity. Thus, we assume that in the presented case, fatal outcome of poisoning with decis was rather connected with toxic effects of hydrocarbon base (solvent naphtha) than with deltamethrin action. In the described case, detection of aromatic hydrocarbons in blood and lung tissue and their metabolites in urine confirms that these substances were absorbed from gastrointestinal tract to the systemic circulation. Predominant among the clinical outcomes in our patient was profound depression of CNS with apnea, which could be connected with narcotic action of organic solvents. The cardiac arrest was in mechanism of asystolia with prior non-responsive to catecholamines bradycardia and vascular collapse. We connect it with hydrocarbon-induced cardiotoxicity. It is worth remembering that many pyrethroid-containing insecticides are formulated in a hydrocarbon base. Intoxication with such preparations should always be considered not only as poisoning with pyrethroid alone but also as intoxication with hydrocarbons.