We review recent results on superhump period variations in SU UMa-type dwarf novae. Our statistical studies have revealed that the evolution of the superhump period is basically composed of three stages: stage-A, during which the superhump period is long and constant, stage-B, during which the superhump period increases as the superoutburst proceeds, and stage-C, during which the superhump period is short and constant. We also introduce a new method of estimating a mass ratio using the stage-A superhump period. This method can extend to, for example, low mass X-ray binaries or AM CVn stars if the stage-A superhump period is well determined.

ABSTRACT
1. INTRODUCTION
2. TEXTBOOK OF SUPERHUMP PERIOD CHANGE
3. A NEW ESTIMATION OF THE MASS RATIO USINGSTAGE-A SUPERHUMP
4. SUMMARY
REFERENCES

• Akira Imada(Tomominami)
• Taichi Kato(Department of Astronomy, Kyoto University)