The original study by Kruger and Dunning was in 1999. You can tell what the study involved just by reading the full name of the paper:
Unskilled and unaware of it: How difficulties in recognizing one’s own incompetence lead to inflated self-assessments.
Since that time, there have been studies that either agreed or disagreed. So, another study was done in 2007 to try to address these issues. This study was by Ehrlinger, Johnson, Banner, Dunning, and Kruger. The paper is entitled:
Why the Unskilled Are Unaware: Further Explorations of (Absent) Self-Insight Among the Incompetent and it contains 73 citations including previous work by the above authors, work done before the 1999 study, and work done since the 1999 paper. Fortunately, that paper is available here:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702783/#R48
If there is any doubt about what this paper involves, let me quote the abstract:
People are typically overly optimistic when evaluating the quality of their performance on social and intellectual tasks. In particular, poor performers grossly overestimate their performances because their incompetence deprives them of the skills needed to recognize their deficits. Five studies demonstrated that poor performers lack insight into their shortcomings even in real world settings and when given incentives to be accurate. An additional meta-analysis
showed that it was lack of insight into their own errors (and not mistaken assessments of their peers) that led to overly optimistic estimates among poor performers. Along the way, these studies ruled out recent alternative accounts that have been proposed to explain why poor performers hold such positive impressions of their performance.
Next, you can easily see what the issues are just by looking at the three section introductions.
1. Section 1 was designed to directly address the claims that apparent over and underestimation among bottom and top performers can be reduced to statistical and methodological artifacts.
Thus, in Part 1,
we looked at real world cases in which people approached (often challenging) tasks that they would encounter anyway in their everyday lives, rather than ones managed by experimenters to seem either easy or difficult.
2. If this is the case, what appears to be an inability to assess the quality of one’s performance on the part of the unskilled might actually be an unwillingness to do so accurately, in that the unskilled prefer to report a rosy view of their performance. Under this analysis, those who are unskilled can and will recognize how poorly they have performed if properly motivated. Thus, in the three studies comprising the second section,
we offered incentives to encourage participants to provide accurate self-assessments. If the unskilled are truly unable to evaluate the quality of their performances, their performance estimates should remain inflated even in the face of strong incentives to be accurate.
3. In Section 3, however, we provide a meta-analysis of existing data to look directly at the specific errors leading to overestimation of comparative performance among poor performers and underestimation by top performers.
If we could tie patterns of over- and underestimation more closely to the types of specific errors predicted by Kruger and Dunning (1999), we would then provide evidence in support of (or against) their account.
The actual experiments, methods, and graphs are in the body of the paper. However, we can skip to the concluding remarks:
Taken together, these findings
reaffirm the notion that poor performers show little insight into the depth of their deficiencies relative to their peers. They tend to think they are doing just fine relative to their peers when, in fact, they are at the bottom of the performance distribution. By now,
this phenomenon has been demonstrated even for everyday tasks, about which individuals have likely received substantial feedback regarding their level of knowledge and skill.
and/or 
