The rupee appreciated by 25 paise to 81.81 against the US dollar in early trade on Monday, tracking positive sentiments in the domestic equity market and subdued dollar against major currencies. At the interbank foreign exchange, the domestic unit opened at 81.78 against the dollar and slipped to 82.06. Later, it gained ground to reach 81.81 registering an increase of 25 paise over its previous close.