Abstract: Over 20 percent of prison and jail inmates in the United States are currently awaiting trial, but little is known about the impact of pre-trial detention on defendants. This paper uses the detention tendencies of quasi-randomly assigned bail judges to estimate the causal effects of pre-trial detention on subsequent defendant outcomes. Using data from administrative court and tax records, we find that being detained before trial significantly increases the probability of a conviction, primarily through an increase in guilty pleas. Pre-trial detention has no detectable effect on future crime, but decreases pre-trial crime and failures to appear in court. We also find suggestive evidence that pre-trial detention decreases formal sector employment and the receipt of employment- and tax-related government benefits. We argue that these results are consistent with (i) pre-trial detention weakening defendants' bargaining position during plea negotiations, and (ii) a criminal conviction lowering defendants' prospects in the formal labor market.