A number of conflict style inventories have been in active use since the 1960s. Most of them are based on the managerial grid developed by Robert R. Blake and Jane Mouton in their Managerial Grid Model. The Blake and Mouton model uses two axes. "Concern for people" is plotted using the vertical axis and "Concern for task" along the horizontal axis. Each axis has a numerical scale of 1 to 9. These axes interact so as to diagram five different styles of management. This grid posits the interaction of task with relationship and shows that according to how people value these, there are five basic ways of interacting with others.
In 1974, Kenneth W.Thomas and Ralph H. Kilmann introduced their Thomas-Kilmann Conflict Mode Instrument (Tuxedo NY: Xicom, 1974). In 1999, CPP, Inc. (Mountain View, CA) acquired Xicom and is now the sole publisher and international distributor of the TKI. The TKI popularized conflict style inventories and, according to the publisher's website, there are over five million copies published, making it the best known of the commercial conflict style inventories. 
The Thomas-Kilmann Conflict Mode instrument consists of thirty pairs of statements. For each pair, the respondent must choose either the A or B item (for example, one item depicts collaborating while the other item describes avoiding). Each pair of statements was specifically designed, through a multi-stage research process, to be equal in social desirability.
The TKI uses two axes (influenced by the Mouton and Blake axes), called "assertiveness" and "cooperativeness". The TKI identifies five different styles of conflict: Competing (assertive, uncooperative) Avoiding (unassertive, uncooperative), Accommodating (unassertive, cooperative), Collaborating (assertive, cooperative), and Compromising (intermediate assertiveness and cooperativeness). This is very similar to other psychometric tools, such as DISC assessment, Social styles, and a theory of Five Temperaments, all of which use similar scales.
A similar inventory is the Kraybill Conflict Style Inventory which is also based on the Mouton-Blake Managerial Grid and identifies five styles of responding to conflict.
The TKI is quick to administer and interpret. It takes about 15 minutes to answer the questions, and about an hour for interpretation by a trainer. Interpretation materials help respondents identify the appropriate use of the styles and help them become more comfortable with styles they are less familiar with. The TKI is widely known and is available in English, French, and Spanish versions.
Compared to some other conflict instruments, the TKI has shown that it reduces the social desirability bias from over 90% to less than 20%. Also, other instruments that do not use a forced-choice format may inadvertently confuse the frequency of using each mode with the amount of conflict in the situation.
Some respondents find the forced choice questionnaire to be frustrating. The questionnaire assumes that all respondents have a similar cultural background. Some trainers report frustration among respondents from minority backgrounds or from outside the United States. Also, the TKI interpretation materials are not extensive.