This is based on joint work with Dominic Joyce and Markus Upmeier. We discuss issues on orientability of the moduli spaces that appear in gauge-theoretic moduli problems; and how to orient those moduli spaces if they are orientable. We begin with backgrounds, motivation and recalling the orientation problem for the anti-self-dual instanton moduli spaces. We then move on to discussisng the problems for other gauge-theoretic moduli spaces with more general framework and techniques; and describe new results on the orientation problems.