I am trying to use the glm.nb proceedure in the new MASS library. I have count data (of snails) taken from a number of habitats (artesian springs). I want to model the abundances, including an effect of the organic content of the sediment. When I try to fit a model like: nb.model.p <- glm.nb(abundance~Organics.per.wt) I get the error message: Error: no valid set of coefficients has been found:please supply starting values I looked in the help for the glm proceedure and found the "start()" statement for specifying coefficients. However, I could not find much documentation on what should be in start. I searched the R website and also didn't find much detail on start(). On a lark I tried the following, just to see if I had the syntax correct: nb.model.p <- glm.nb(abundance~Organics.per.wt,start=(1,1)) which I did not. I had a look in Venables and Ripley, but could not find an example there either. So if anyone can point me in the direction of the proper documentation or provide any helpful input I would greatly appreciate it. Thanks, Chris Wilcox Dr. Chris Wilcox Research Fellow Department of Zoology and Entomology University of Queensland St. Lucia 4072 QLD Australia email: c.wilcox at uq.edu.au tel: 61.7.3365.1686 fax: 61.7.3365.1655 website: www.uq.edu.au/~uqcwilco "In God we trust all others must bring data" W. Edwards Deming