  We consider the six dimensional hypermultiplet, vector and tensor multiplet
models in (1,0) harmonic superspace and discuss the corresponding superfield
actions. The actions for free (2,0) tensor multiplet and for interacting
vector/tensor multiplet system are constructed. Using the superfield
formulation of the hypermultiplet coupled to the vector/tensor system we
develop an approach to calculation of the one-loop superfield effective action
and find its divergent structure.
