This paper deals with the average order of arithmetic functions a(n) w
ith a generating function of the shape (1.1) where f(k) and g(j) posse
ss certain characteristic properties of the zera-function. Under fairl
y general conditions, a lower bound for the error term in the asymptot
ic formula for the corresponding Dirichlet summatory function is estab
lished. Finally, several specific applications to functions from eleme
ntary number theory and to arithmetic problems in number fields are di
scussed.