Uncertified commercial research animal feed (Purina Chow TM) was analyzed over forty-one months to determine essential and trace elements and toxic contaminants. Parametric statistics and graphic chronologic progressions of the results are presented for cat, monkey, rodent (rat/mouse), guinea pig and dog diets. Concentrations of toxic contaminants are discussed in terms of Maximum Allowable Concentrations (MAC) proposed by EPA. The impact of undesirable contaminants on in vivo animal studies in analyzed. Practical aspects of cost-effectiveness of feed analysis in a major research setting is discussed.