The stability of the enzyme urease to the aerosolization process was evaluated. The effect of liquid feed rate, operating pressure, gas composition and relative humidity on urease enzymatic activity were studied using a Constant Output Atomizer operated in the non-recirculating (i.e. single-pass) mode. The results show that changes in the liquid feed rate had the greatest influence on subsequent urease enzymatic activity. Relative humidity of the supply gas also played an important role through its influence on solution evaporation rate and resultant protein concentration in the solution. Operating pressure and gas composition had only minor effects. Additional experiments run with a Collison nebulizer operating in the recirculating (multi-pass) mode indicated a time-dependent loss of urease activity. On average, 50% of the initial activity was left in the nebulizer solution after 10 min of operation. The introduction of protective additives to the solution helped to reduce degradation.