I'll give an update on the key cosmological analysis of Dark Energy Survey Year 1 data, in which galaxy clustering and weak lensing information are combined to produce highly competitive cosmological constraints. As well as providing complementary cosmological information, this multi-probe analysis breaks degeneracies between systematics, such as galaxy intrinsic alignments, and cosmological parameters. After a brief introduction to the theory, I will discuss some of challenges we have faced in controlling systematics at the required level for this complex and high precision analysis. I will demonstrate the approach we have taken to ensuring the robustness of our results, including extensive validation on mock survey data. I will show forecasted and/or blinded cosmological parameter constraints.