Adhi Yoga is one of the favourable or Subha Yogas expounded in Vedic Astrology. 

Two forms of the Yoga
There are two ways in which the Adhi Yoga arises. One way is reckoning the positions of relevant planets from the Moon sign and the other is doing so from the Ascendant. 
The occupation of the three benefics, Jupiter, Venus and Mercury in the 6th ,7th, and the 8th Houses from the Moon sign gives rise to Chandradhi Yoga and the occupation of these three planets from the Lagna constitutes the Lagnadhi Yoga.   However, the results of both forms of the Yoga are considered the same. 

Opinions of ancient sages 
According to Indian sage Parasara benefics occupying any of the three Houses, 6th, 7th or the 8th would give rise to this yoga. The sage Mandavya also holds the same view.  However, Indian Guru Vaidyanatha says that in the case of the Lagnadhi Yoga, that the 4th House from the Ascendant should be free from the occupation of any malefic planets if the yoga is to come to fruition even if the benefics occupy the 6th, 7th and 8th Houses.  In fact, this is a premise upheld by the Jaimini school of Astrology. 

However, it is widely accepted that the Adhi Yoga is rendered less effective if the malefics conjoin the malefics. The malefics are Sun, Mars and Saturn in the ascending order of the maleficence. 

The Adhi Yogas are generally classified as follows: 
Three benefics (Jupiter, Venus and Mercury) are in one House, 6th, 7th, or the 8th from the Ascendant.
Two benefics in any two of the 6th, 7th and the 8th Houses from the Ascendant
Thee benefics in all the above-mentioned three Houses from the Moon sign
Three benefics in any two of the above mentioned three Houses from the Moon
Two benefics in any two of the above mentioned three Houses from the Moon
Two benefics in any two Houses of the aforementioned three Houses from the Ascendant or the Moon 
One benefic in any one House of the aforementioned three Houses from the Ascendant or the Moon. 
An Adhi Yoga is fully effective when all the three benefics are involved, medium with two benefics and ordinary when only one benefic involved. 

Results of Adhi Yoga
The results of Adhi Yoga: Native would be (a)a Minister of State (b) a top civil servant (c) a medical consultant (d) a high prelate (e) an engineer (f)a banker (g) a billionaire (h) an author (I) a musician (j) an astrologer (k) an artiste or (l) an individual enjoying long life and good health.

The results from (a) to (e) could be attributed to Lagnadhi Yoga and the remaining ones to the Chandradhi Yoga.  One could enjoy long life and good health if any one of the three benefics is well placed in any one of the three Houses, 6th, 7th or the 8th from the Ascendant or the Moon.