We compare estimates of peer effects on worker output in laboratory experiments and field studies from naturally occurring environments. The mean study-level estimate of a change in a worker's productivity in response to an increase in a co-worker's productivity (gamma) is (gamma) over cap = 0.12 (SE = 0.03, n(studies) = 34), with a between-study standard deviation tau = 0.16. The mean estimated (gamma) over cap -values are close between laboratory and field studies ((gamma) over cap (lab) - (gamma) over cap (field) = 0.04, P = 0.55, n(lab) = 11, n(field) = 23), as are estimates of between-study variance tau(2) ((tau) over cap (2)(lab) - (tau) over cap (2)(field) = -0: 003, P = 0.89). The small mean difference between laboratory and field estimates holds even after controlling for sample characteristics such as incentive schemes and work complexity ((gamma) over cap (lab) - (gamma) over cap (field) = 0.03, P = 0.62, n(samples) = 46). Laboratory experiments generalize quantitatively in that they provide an accurate description of the mean and variance of productivity spillovers.