The average content of microelements (ME) in crude oils and gas condensates (GC) is given, as well as their average content in the condensation waters of gas and gas-condensate fields. It is shown that, in the case of the entry of natural gas into an oil formation and its subsequent dissolution, ME are added to the crude oil, altering its initial microelemental composition, The introduction of ME into the erode oil depends on the content of high-boiling hydrocarbons (HC) and water vapour in the formation gas, and also on the amount of gas dissolving in 1 t of crude oil under the temperature and pressure conditions in the formation. For the case of the formation mixtures of three gas-condensate fields (GCF), and also the formation mixture of a hypothetical gas field, an estimate is made of the quantities of 32 ME entering crude oil with dissolving gas.