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Setup using a simple example: I've got 1 table ( Totals ) that holds the sum of the amount column of each record in a second table ( Things ). When a thing.amount gets updated, I'd like to simply add the difference between the old value and the new value to total.sum . Right now I'm subtracting self.amount during before_update and adding self.amount during after_update . This places WAY too much trust in the update succeeding. Constraint: I don't want to simply recalculate the sum of all the transactions. Question: Quite simply, I'd like to access the original value during an after_update callback. What ways have you come up with do this? Update: I'm going with Luke Francl's idea. During an after_update callback you still have access to the self.attr_was values which is exactly what I wanted. I also decided to go with an after_update implementation because I want to keep this kind of logic in the model. This way, no matter how I decide to update transactions in the future, I'll know that I'm updating the sum of the transactions correctly. Thanks to everyone for your implementation suggestions.

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