The iguana needs to be 10-12 inches long before gender can be determined visually, and often we still cannot be accurate. Take a look at the 3 posts at the top of the "Gender Issues" forum. The shape of the head, size of the femoral pores, and presence or lack of hemipenal bulges are the most indicative attributes. There are some great male/female pics for comparison in those 3 posts.
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