Dear List, Thanks for all the good suggestions. Here's how my fit stands at this point. I have a few multiple scattering paths at 3.989, in order to excude these 2 I put the R-range from 1-3.975. It seems that you think I should include these paths, if so, do I treat them a little differently. They don't seem to help the fit using the same parameter strategy. Additionally, I extended the k-range from 2-13.5 to 2-15. This seemed to improve the reduced chi-square dramatically. Thanks Again, Dan One Eo, seperate ss's, seperate Delr's, expanded k, R ranges: Independent points = 24.281250000 Number of variables = 7.000000000 Chi-square = 6436.437226455 Reduced Chi-square = 372.452063737 R-factor = 0.047313433 Measurement uncertainty (k) = 0.000187262 Measurement uncertainty (R) = 0.006509968 Number of data sets = 1.000000000 Guess parameters +/- uncertainties (initial guess): ss = 0.0041180 +/- 0.0005120 (guessed as 0.004636 (0.000411)) e0 = 0.8351420 +/- 1.1214120 (guessed as 1.765958 (1.154388)) alpha = -0.0012160 +/- 0.0030000 (guessed as 0.001090 (0.002843)) ss2 = 0.0044650 +/- 0.0004590 (0.0000) ss3 = 0.0284980 +/- 0.0234700 (0.0000) alpha2 = 0.0070700 +/- 0.0020190 (0.0000) alpha3 = -0.0267670 +/- 0.0318320 (0.0000) Def parameters: delr_1 = -0.0048260 delr_2 = 0.0280560 delr_3 = -0.1062180 Set parameters: amp = 0.7 Correlations between variables: e0 and alpha --> 0.8148 e0 and alpha2 --> 0.6596 alpha and alpha2 --> 0.5393 ss3 and alpha3 --> 0.3825 e0 and alpha3 --> -0.2940 All other correlations are below 0.25