Parivartana yogas are the mutual exchanges of sign, in which the lord of one house sits in a second house whose lord sits in the first. The classical treatment divides them into three grades. Maha parivartana, the great exchange, involves houses none of which is the sixth, eighth or twelfth, and is read favourably, binding the two houses to one another's advantage. Kahala parivartana involves the third house with certain others and is read as mixed. Dainya parivartana involves one of the three dusthanas and is read unfavourably, as difficulty in one area dragging on another. The technique is prized for its clarity: unlike most yogas it requires no judgment of planetary strength to identify, only the positions of two lords, and its result, that the affairs of two houses become interdependent, is unusually specific.
Phaladeepika, one of the texts most often cited for the graded classification given above, is attributed to Mantreswara, whose own date is disputed among scholars, with estimates ranging from the thirteenth to the sixteenth century and the sixteenth generally favoured; the Sanskrit text itself was not printed until the early twentieth century. A principle attributed to the earlier text Saravali, by Kalyana Varma, and repeated in later summaries though not confirmed here against the primary Sanskrit, holds that two planets in mutual exchange act as though they were conjunct in either of their two houses, one way later commentators explain why a maha parivartana between two strong houses is read as being nearly as powerful as an actual conjunction of their lords.