Periodic Pledges can be made via Credit Card (Visa, Mastercard, or Discover) or Paypal. You can select the amount and how frequently you'd like your automatic donations to be made (minimum $10 per installment).

Periodic pledges qualify as the Erowid membership level appropriate to the value donated in a year. Membership gifts can be requested after your contributions reach the required total for the gift you'd like to receive (i.e. if you pledge $10/mo, and would like a t-shirt, you can request the shirt after the fifth month, when your donated total exceeds $50, the minimum for a shirt).