Using a $t$-norm $T$, the notion of $T$-fuzzy
topological subalgebras in $BCK$-algebras is introduced, and the
fact that $T$-fuzzy subalgebras of a $BCK$-algebra $X$ form a
complete lattice is proved. Using a chain of subalgebras,
a $T$-fuzzy subalgebra is established. Some of Foster's results on
homomorphic image and inverse image to $T$-fuzzy topological subalgebras
are considered.