Peroxyformic acid has been recently assuming a growing importance due to the versatile oxidizing properties in several applications in the chemical industry. However, quite surprisingly, a lack of data exists about the kinetics of formation of this compound, an even more singular event considering that the acid, when used, is generally produced in situ via the reaction between formic acid and hydrogen peroxide. This paper is a contribution to fill this gap. A series of batch experiments were carried out to measure the conversion rate in the peroxyformic acid formation reaction in the temperature range 30-60 degrees C. The results from experiments were successfully interpreted through a kinetic mechanism consisting of the reversible formation of the peroxyformic acid and its irreversible decomposition to CO2 and H2O, both catalyzed by hydrogen ions. With the considered kinetic mechanism, a pre-exponential factor of 13065.1 L-6 mol(-2) s(-1) and an activation energy of 43524.2 J mol(-1) were calculated. This last value and enthalpy and entropy of reaction derived from the kinetic data are in quite good accordance with the limited literature data available on this subject.