Technical Abstract: This research examined the optimal dry period length (the period between lactations when a cow is not being milked) to maximize milk yield across adjacent lactations and lifetime yield. Lifetime yield not only accounts for loss of production in the lactation preceding the dry period, but also accounts for any detrimental or beneficial consequences of days dry on total days in the herd. This article is intended for a national dairy publication, and is, therefore, important to dairy producers and their management strategies.