The Compatibility Quotient (CQ) is an index of similarity within established or potential couples across a variety of domains known to predict long-term relationship success. Validation data has been presented showing that established couples have substantially higher CQ scores than randomly paired couples and that couples with rewarding relationships have higher CQs than those whose relationship is less happy. Here we show that CQ scores predict desire to pursue a relationship after only a brief speed-date encounter. Nineteen young men had 3-minute social exchanges with 19 young women, providing data on 361 potential relationships. Those couplings in which both parties expressed a desire at least for friendship showed mean CQs of 107.7, compared with a mean of 102.7 for couplings in which at least one party had no desire for further contact (p < 0.001). The CQ was also predictive of immediate physical attraction. Mutually attracted couples averaged CQs of 108.0 compared with 101.2 for those not attracted to each other (p < 0.01). These effects were apparently driven by female preferences, with males being less discriminating.