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Shettles method What it isTimed intercourse on specific days of your cycle.EffectivenessShettles proponents claim the technique is 75 percent effective, but other experts dispute this. Keep in mind that you always have about a 50 percent chance of conceiving the sex you want.How it's doneThe theory is that sperm bearing Y chromosomes (for boys) move faster but don't live as long as sperm that carry X chromosomes (for girls). So if you want a boy, the Shettles method argues, you should have sex as close as possible to ovulation. If you want a girl, you should have sex two to four days before you ovulate.Pros• Requires no drugs or invasive medical procedures.• Free or low cost.• Relatively safe.Cons• You must take your basal body temperature every day to figure out when you're ovulating, or use an ovulation prediction kit.• There's no guarantee of success.AvailabilityAnyone can try it.For more information• Learn more about charting your basal body temperature and ovulation predictor kits.• Read How to Choose the Sex of Your Baby, by Landrum Shettles, M.D., and David Rorvik.   Whelan method What it isTimed intercourse on specific days of your cycle.EffectivenessWhelan claims her technique is 68 percent effective for boys and 56 percent effective for girls, but many experts dispute this. Keep in mind that you always have a 50 percent chance of conceiving the sex you want.How it's doneThe Whelan method directly contradicts the Shettles method. The theory here is that biochemical changes that may favor boy-producing sperm occur earlier in a woman's cycle. So if you want a boy, you should have intercourse four to six days before your basal body temperature goes up. If you want a girl you should have sex two to three days before you ovulate.Pros• Requires no drugs or invasive medical procedures.• Free or low cost.• Safe.Cons• You must take your basal body temperature every day to figure out when you're ovulating, or use an ovulation prediction kit.• There's no guarantee of success.AvailabilityAnyone can try it at home.For more information• Learn more about charting your basal body temperature and ovulation predictor kits.• Read Boy or Girl? by Elizabeth Whelan.   Sex-selection kits What it isThese at-home kits are based on the Shettles theory. Separate girl and boy kits include a thermometer, ovulation predictor test sticks, vitamins, herbal extracts, and douches that are supposedly gender specific.EffectivenessKit makers claim a 96 percent success rate. But the American Society for Reproductive Medicine tells consumers not to bet on it. Some medical experts go a step further and say the kit maker's claims are without scientific merit.How it's doneYou track your cycle using the thermometer and ovulation predictor test sticks (which you urinate on). Following the Shettles method, you have intercourse two to four days before ovulation if you want a girl and as close as possible to ovulation if you want a boy. The douche is intended to change the vaginal environment to "influence the chances that either an X-carrying sperm or a Y-carrying sperm will be successful in fertilizing the egg." Vitamins and herbal extracts are also included to supposedly boost your odds of getting the gender of your choice.Pros• Requires no invasive medical procedures.• Convenient.Cons• The success rate claimed by the makers is questionable.• ExpensiveCost $199 for a 30-day kit.AvailabilitySex-selection kits are available through GenSelect.For more informationLearn more about sex-selection kits at GenSelect's Web site.