The Hippocratic Oath

I swear by Apollo the physician, and Aesculapius, Hygeia and Panacea and all the gods and goddesses, that, according to my ability and judgement, I will keep this Oath and this covenant.

To reckon him who taught me this Art equally dear to me as my parents, to share my substance with him, and relieve his necessities if required; to look upon his offspring on the same footing as my own brothers, and to teach them this Art, if they shall wish to learn it, without fee or stipulation; and that by precept, lecture, and every other mode of instruction, I will impart a knowledge of the Art to my own sons, and those of my teachers, and to disciples who have signed the covenant and have taken an oath according to the law of medicine, but no one else.

I will follow that system of regimen which, according to my ability and judgment, I consider for the benefit of my patients, and abstain from whatever is deleterious and mischievous.  I will give no deadly medicine to anyone if asked, nor suggest any such counsel; and in like manner I will not give to a woman an abortive remedy. With purity and with holiness I will pass my life and practise my Art.

I will not cut persons labouring under the stone, but will leave this to be done by such men as are practitioners of this work.  Into whatever houses I enter, I will go into them for the benefit of the sick, and will abstain from every voluntary act of mischief and corruption; and, further, from the seduction of females or males, of freemen and slaves.
 

Whatever, in connection with my professional practice, or not in connection with it, I see or hear, in the life of men, which ought not to be spoken of abroad, I will not divulge, as reckoning that all such should be kept secret.  While I continue to keep this Oath unviolated, may it be granted to me to enjoy life and practice of the Art, respected by all men, in all times. But should I trespass and violate this Oath, may the reverse be my lot.

Source: http://www.usmedstudents.com/links/hippocraticoath.htm
A Modern Physicians Oath
The World Medical Association

At the time of my being admitted as a member of my profession, I solemnly pledge myself to consecrate my life to the service of humanity;

I will give to my teachers the respect and gratitude which is their due; I will practise my profession with conscience and dignity;

The health of those in my care will be my first consideration; I will respect the secrets that are confided in me, even after a patient has died;

I will maintain by all the means in my power the honour and the noble traditions of my profession; My colleagues are my sisters and brothers;

I will not permit considerations of age, disease or disability, creed, ethnic origin, gender, nationality, political affiliation, race, sexual orientation or social standing to intervene between my duty and my patient;

I will maintain the utmost respect for human life from its beginnings, even under threat, and I will not use my specialist knowledge contrary to the laws of humanity;

I make these promises solemnly, freely and upon my honour.
This oath was adopted in Geneva in 1948, and amended in Sydney in 1968 and in Liverpool in 1995.  Please note:  Contrary to popular belief, the majority of new physicians do not take any oath upon receiving their diplomas or certifications.