Relative viscosities for formic, acetic, propionic and butyric acids in aqueous solutions were determined using thermostatic Ubbelohde flow viscometer in temperature range of 25 to 65-degrees-C. Excess viscosity, excess volume and activation parameter were calculated. It seems that as excess volume decreases with the rise of mole fraction of the particular acid and the corresponding excess viscosity increases. The effect of temperature on excess viscosity is much more telling than the same effect on DELTA-V(E). The explanation of this behaviour appears to be in the fact that with rise of temperature the intermolecular forces between acid-acid, acid-solvent and solvent-solvent change significantly to effect the viscosity behaviour, whereas for excess interactions as a function of temperature seems to get in different directions. This behaviour is well known for a liquid containing hydrogen bonds.