Lactation records of US Holstein cows were analyzed with mixed models to determine the effect of dystocia on 305-d milk, fat, and protein yields, days open, number of services, and cow losses and to estimate the economic loss associated with dystocia. The data were 122,715 records of 71,618 cows from 1980 to 1991. The single-trait animal model included herd-year-season, sex of calf, age of dam, and dystocia score as fixed effects and animal and permanent environment as random effects. The effect of dystocia was significant (P < 0.01) on all traits within and across parities. Over multiple parities, the differences between score 5 (extreme difficulty) versus score 1 (no problem) for milk yield, fat yield, protein yield, days open, number of services, and cow deaths were 703.6 kg, 24.1 kg, 20.8 kg, 33 d, 0.2 services, and 4.1%, respectively. The losses associated with traits were priced and summed to determine the total economic loss associated with dystocia. In addition, calf mortality was considered to be a cost. Across parities, estimates of costs were $0.00, $50.45, $96.48, $159.82, and $379.61 for scores 1 to 5, respectively. Cost of dystocia was relatively higher on a per incidence basis than would be expected from the mean of the population. The total cost associated with dystocia (i. e., within-parity sum of costs associated with dystocia scores weighted by the probability of occurrence) was $28.53 for an average heifer and about $10.00 for an average cow for other parities.