My late teens I believe, my mother was an atheist and my father was unsure but as a family it was never discussed around the dinner table. We all just kept our opinions to ourselves.

I first questioned my beliefs when I was younger than 10. I was brought up in a Christian cult. Being sexually abused and not protected, as promised in the bible, started my doubt. I was an adult before I told people I was agnostic. It began with teaching my children about every religion instead of just one. I taught them that way so that they could make up their own minds rather than being forced to traditionally/blindly follow in set footsteps. I have 3 children (ages 15,17, & 18) and to date there is one Christian (which is what the rest of my family is), and two agnostics. I'd say I raised them pretty damned good

I must've been around 14-15 when I first really started to question the existence of God. Some would argue that it wasn't God I was questioning, but the hypocrisies I saw in the religious sects that were around me, including my own. So I may not have been questioning God at that point but the people that claim to follow his teachings.
But like many of you have suggested, there were many unanswered questions, or one's that were answered with "That's why we have 'faith'" along the way.
It wasn't until later that I even knew or understood the words agnostic and atheist, and at times have used both to describe my condition. But the reality is that I leave myself open-minded to doubt leaving me an agnostic by definition.

As long as I can remember. Certainly by the time I was in primary school.

God just never made any sense to me. I didn't tell people I was an atheist as I didn't know the word, but I did tell teachers, parents and the local vicar that I didn't believe their stories.

I think I was about 14 when I started condemning religion. At high school one day some wannabe cowboy was fucking with me about my Led Zeppelin shirt, I told him that I was his god. After that I became more vocal on my stance.

I was in my late teens, but I "came out" as atheist when I was 23.

I did a double whammy to my Mormon parents. I was in effect coming out as a gay man, but I had no deasire to go through religious arguments, so I also came out as atheist at the same time. Rather than fight a war, I chose to first take away all their weapons they would use against me. I was already atheist, I just let then know that at the same time I let them know I was gay.

In case anyone readign this wonders, the strategy worked well for me. I came out via a letter, because I figured if we talked in person or on the phone then things might get said that could not be taken back. Over time they accepted it up to a point. We were never really close anyways, and in the end nothign really changed in our relationship.

Hi.Church Sunday school was always a bore to me.I never believed what I was being told.If I was ever asked I would say I was Church of England.Since educating myself on the arguments to counter the Christian belief,I'm confident to tell anybody that I'm an atheist.Been that way for 40 years.

From the first Fuck You? I am a self made kind of guy that figure out answers to my questions while attending catholic school and finding comfort in the act of sin to the point of being cussed out by priests and nuns. Not even now I am going around with chip on my shoulder... Is not that important, because never was... I just am. I know I am a cardholder but I don't carry a card.