B. W. Tuckman’s model of small group development proposes that groups progress through four formative stages widely known under the mnemonic “forming, storming, norming, performing.” This article analyzes 10 small software development teams classified by age, size, managerial and technical skill, reporting and communication structure, and process performance as assessed under the capability maturity model. Software development teams differ from the experimental groups studied by Tuckman and others in that they often remain together for years to develop, maintain, and enhance a product. The data suggest the need for an extended stage model of team formation that includes analogous decay stages: denorming, de-storming, de-forming. The data support a pattern of increasing and decreasing performance that mirrors the formation and dissolution of teams.