Are they sinful? Well, not technically, but like anything they can be if they are used just to exhibit rebellion or something along those lines. However, even the "non-sinful" ones, I really would not recommend for 3 reasons 1) the health hazarads that are sometimes involved. For instance, tongue piercings often are suseptible to infection. I am a female and even having my ears pierced at a reputable location, I continually had ear infections for years until I finally just let the holes grow in. I have known other women with the same problem. Likewise, people who get tatoos can not give blood for 1 year due to the risk that they may have obtained HIV from it. Of course, the chances are slim, but not every place has high hygiene standards so infection and even HIV is possible with getting a tatoo. 2) tatoos are something that people often regret later in life but they are not like makeup that can be washed off. It is a decision that can last a lifetime unless one gets it surgically removed. I don't know enough about body piercing to know if a tongue or navel will permanently have holes but I would encourage someone to find out before they made the leap. 3) One does have to consider how society views these things. Will it interfere with one getting a professional job? Will it interfere with one getting a mate? Will it mar one's witness for God? etc. The truth is many people associate tatoos with gangs or rebels. Not everyone makes that association but one can not avoid the fact that many people do. I now live in a country where people with tatoos are banned from public pools, restaurants, hotels, etc. because tatoos are associated with the underworld. Body piercings are not as strickly prohibited but the people who have them are certainly frowned upon. I think bringing this kind of wrath on oneself is just not worth it. There is some wrath worth going through like standing up for one's faith or standing up for a weak person, but other wrath is just not worth it in my opinion. If my son came to me asking if he could get a tatoo or have his body pierced, I think I would first ask him to do some research on it so he would be making an informed decision (knowing the risk factors, knowing the proper places to go to have these done, etc.). If after doing some research and he still wanted this, then I would ask him to now examine himself as to why he wanted this. Is it something he really wanted? or was it something he just wanted to have to look cool for the moment and would he still want it 30-40 years from now? Does he feel like he could glorify God through this? Had he prayed about it? etc. I just feel like it is something one should really give some good thought to before just running out and doing it. I think with careful consideration, most people would conclude it is not the best decision, but if they did honestly conclude it was a good thing, then I don't think God would be angry at them.