I hear a lot more dreams from women than from men, so my sample is skewed, but I’ve heard many dreams in which the female dreamer dreams she’s a man and not many at all from men who’ve dreamed of being a woman. However, I expect that similar themes are at play in both versions of this dream.
I’ve had many dreams of being a man. Sometimes this is just a knowing I have in the dream, like the one where I was chasing a streetcar. All the focus was outward, but I clearly knew that I was a man in the dream. In other dreams, the focus is on the distinguishing anatomy, which carries further levels of association.
For the first kind of dream, for me the knowledge that I’m a man in the dream suggests that I’m integrating masculine and feminine roles or energies. While it’s a metaphorical construct to define masculine as action oriented and decisive and feminine energy as receptive and nurturing, it can be a useful construct for examining this type of dream. If I dream I’m the opposite sex, perhaps I’m discovering parts of myself that I somehow feel “belong” with the opposite anatomy. One suggestion is to make a list of qualities, faults, and characteristics you associate with “men” and “women” and to see what on that list feels comfortable and familiar and what feels more alien. Which characteristics come into play in the dream?
To dream specifically of genitalia can of course carry all sorts of personal associations, but on a more archetypal level, the penis is associated with the power to impregnate, to provide the spark that brings something to life. It suggests potency and the ability to take action. The vulva is receptive and/or devouring, the gateway of birth and blood. Depending on the context of the dream, of course, this suggests the ability to take something in and nurture until it’s ready to enter the world.