Abstract. A new construction for the form sum of positive, selfadjoint operators is given in this paper. The situation is a bit more general, because our aim is to add positive, symmetric operators. With the help of the used method, some commutation properties of the form sum extension are observed.

AMS Subject Classification (1991): 47A20, 47B25

Received July 18, 2000, and in revised form June 25, 2001. (Registered under 2817/2009.)