I wrote to William Hrushevsky, MD one of the lead researchers in the area of timing. Here is what he said in response to my questions. I said for the SAKE OF DISCUSSION THAT MY PERIOD STARTED ON APRIL 8. 1. If your cycle is, on average, 28 days long, the best time for biopsy or surgery would be ~ 14 days from the first day of menstrual bleeding through ~ 21 days from that first day of menstrual bleeding (April 22 through April 29). 2. If your cycle is an average of 21 days in length, (because the second half of the cycle is still always ~14 days long) the best dates would be from ~ April 15 through April 22. 3. If your cycle is, on average, 32 days long, then your biopsy or surgery should be planned between ~ April 26 and May 4. The reason for this is that the luteul phase of the cycle ovulation to the first day of bleeding of the next cycle requires ~ 14 days, regardless of cycle duration. All (>85%) of the variability resides in the other half (follicular phase) of the cycle from the first day of bleeding to ovulation. Thereby, the calculation requires both the first day of bleeding and the average cycle duration. You add the average cycle duration in days to the date of the first menstrual bleeding and then subtract 14 days. Voila! Bill William J.M. Hrushesky, MD Breast Cancer Res & Treatmnet, 9/02 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.